Secret writing in the past Francis Bacon 1605 Francis Bacon 1605 Of the Proficience and Advancement of Learning Divine and Humane Bacon’s three cryptographic principles For CYPHARS; they are commonly in Letters or Alphabets, but may bee in Wordes. The kindes of CYPHARS, (besides the SIMPLE CYPHARS with that they be not laborious to write and read; User-friendly 1 Changes, and intermixtures of NVLLES, and NONSIGNIFICANTS) are that they be impossible to discipher; Secure 2 many, according to the Nature or Rule of the infoulding: WHEELE-CYPHARS, KAY-CYPHARS, DOVBLES, &c. But the vertues of them, whereby they are to be preferred, are three; that they be not laborious to write and reade; that they bee impossible to discypher; and in some cases, that they bee without suspition. The highest Degree whereof, is to write OMNIA PER OMNIA; which is vndoubtedly possible, with a proportion Quintuple at most, of the writing infoulding, to the writing infoulded, and no other restrainte whatsoever. This Arte of Cypheringe, hath for Relatiue, an Art of Discypheringe; by supposition vnprofitable; but, as things are, of great vse. For suppose that Cyphars were well mannaged, there bee Multitudes of them which exclude the Discypherer. But in regarde of the rawnesse and Vnskilfulnesse of the handes, through which they passe, the greatest Matters, are many times carryed in the weakest CYPHARS. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 6 / 31
Secret writing in the past Francis Bacon 1605 Francis Bacon 1605 Of the Proficience and Advancement of Learning Divine and Humane Bacon’s three cryptographic principles For CYPHARS; they are commonly in Letters or Alphabets, but may bee in Wordes. The kindes of CYPHARS, (besides the SIMPLE CYPHARS with that they be not laborious to write and read; User-friendly 1 Changes, and intermixtures of NVLLES, and NONSIGNIFICANTS) are that they be impossible to discipher; Secure 2 many, according to the Nature or Rule of the infoulding: WHEELE-CYPHARS, KAY-CYPHARS, DOVBLES, &c. But the vertues of them, whereby they are to be preferred, are three; that they be not laborious to write and reade; that they bee impossible to discypher; and in some cases, that they bee without suspition. The highest Degree whereof, is to write OMNIA PER OMNIA; which is vndoubtedly possible, with a proportion Quintuple at most, of the writing infoulding, to the writing infoulded, and no other restrainte whatsoever. This Arte of Cypheringe, hath for Relatiue, an Art of Discypheringe; by supposition vnprofitable; but, as things are, of great vse. For suppose that Cyphars were well mannaged, there bee Multitudes of them which exclude the Discypherer. But in regarde of the rawnesse and Vnskilfulnesse of the handes, through which they passe, the greatest Matters, are many times carryed in the weakest CYPHARS. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 6 / 31
Secret writing in the past Francis Bacon 1605 Francis Bacon 1605 Of the Proficience and Advancement of Learning Divine and Humane Bacon’s three cryptographic principles For CYPHARS; they are commonly in Letters or Alphabets, but may bee in Wordes. The kindes of CYPHARS, (besides the SIMPLE CYPHARS with that they be not laborious to write and read; User-friendly 1 Changes, and intermixtures of NVLLES, and NONSIGNIFICANTS) are that they be impossible to discipher; Secure 2 many, according to the Nature or Rule of the infoulding: WHEELE-CYPHARS, KAY-CYPHARS, DOVBLES, &c. But the vertues of them, whereby they are to be preferred, are three; that they be not laborious to write and reade; that they bee impossible to discypher; and in some cases, that they bee without suspition. The highest Degree whereof, is to write OMNIA PER OMNIA; which is vndoubtedly possible, with a proportion Quintuple at most, of the writing infoulding, to the writing infoulded, and no other restrainte whatsoever. This Arte of Cypheringe, hath for Relatiue, an Art of Discypheringe; by supposition vnprofitable; but, as things are, of great vse. For suppose that Cyphars were well mannaged, there bee Multitudes of them which exclude the Discypherer. But in regarde of the rawnesse and Vnskilfulnesse of the handes, through which they passe, the greatest Matters, are many times carryed in the weakest CYPHARS. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 6 / 31
Secret writing in the past Francis Bacon 1605 Francis Bacon 1605 Of the Proficience and Advancement of Learning Divine and Humane For CYPHARS; they are commonly in Letters or Alphabets, but may bee in Bacon’s three cryptographic principles Wordes. The kindes of CYPHARS, (besides the SIMPLE CYPHARS with that they be not laborious to write and read; User-friendly 1 Changes, and intermixtures of NVLLES, and NONSIGNIFICANTS) are that they be impossible to discipher; Secure 2 many, according to the Nature or Rule of the infoulding: (in some cases) that they be without suspicion. 3 WHEELE-CYPHARS, KAY-CYPHARS, DOVBLES, &c. But the vertues of Hidden i.e. steganography them, whereby they are to be preferred, are three; that they be not laborious to write and reade; that they bee impossible to discypher; and in some cases, that they bee without suspition. The highest Degree whereof, is to write OMNIA PER OMNIA; which is vndoubtedly possible, with a proportion Quintuple at most, of the writing infoulding, to the writing infoulded, and no other restrainte whatsoever. This Arte of Cypheringe, hath for Relatiue, an Art of Discypheringe; by supposition vnprofitable; but, as things are, of great vse. For suppose that Cyphars were well mannaged, there bee Multitudes of them which exclude the Discypherer. But in regarde of the rawnesse and Vnskilfulnesse of the handes, through which they passe, the greatest Matters, are many times carryed in the weakest CYPHARS. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 6 / 31
Secret writing in the past Francis Bacon 1605 Francis Bacon 1605 Of the Proficience and Advancement of Learning Divine and Humane For CYPHARS; they are commonly in Letters or Alphabets, but may bee in Bacon’s three cryptographic principles Wordes. The kindes of CYPHARS, (besides the SIMPLE CYPHARS with that they be not laborious to write and read; User-friendly 1 Changes, and intermixtures of NVLLES, and NONSIGNIFICANTS) are that they be impossible to discipher; Secure 2 many, according to the Nature or Rule of the infoulding: (in some cases) that they be without suspicion. 3 WHEELE-CYPHARS, KAY-CYPHARS, DOVBLES, &c. But the vertues of Hidden i.e. steganography them, whereby they are to be preferred, are three; that they be not laborious to write and reade; that they bee impossible to discypher; and in some cases, that they bee without suspition. The highest Degree whereof, is to write OMNIA PER OMNIA; which is vndoubtedly possible, with a proportion Quintuple at most, of the writing infoulding, to the writing infoulded, and no other restrainte whatsoever. This Arte of Cypheringe, hath for Relatiue, an Art of Discypheringe; by supposition vnprofitable; but, as things are, of great vse. For suppose that Cyphars were well mannaged, there bee Multitudes of them which exclude the Discypherer. But in regarde of the rawnesse and Vnskilfulnesse of the handes, through which they passe, the greatest Matters, are many times carryed in the weakest CYPHARS. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 6 / 31
Secret writing in the past Francis Bacon 1605 Francis Bacon 1605 Of the Proficience and Advancement of Learning Divine and Humane For CYPHARS; they are commonly in Letters or Alphabets, but may bee in Bacon’s three cryptographic principles Wordes. The kindes of CYPHARS, (besides the SIMPLE CYPHARS with that they be not laborious to write and read; User-friendly 1 Changes, and intermixtures of NVLLES, and NONSIGNIFICANTS) are that they be impossible to discipher; Secure 2 many, according to the Nature or Rule of the infoulding: (in some cases) that they be without suspicion. 3 WHEELE-CYPHARS, KAY-CYPHARS, DOVBLES, &c. But the vertues of Hidden i.e. steganography them, whereby they are to be preferred, are three; that they be not laborious to write and reade; that they bee impossible to discypher; and in some cases, that they bee without suspition. The highest Degree whereof, is to write OMNIA PER OMNIA; which is vndoubtedly possible, with a proportion Quintuple at most, of the writing infoulding, to the writing infoulded, and no other restrainte whatsoever. This Arte of Cypheringe, hath for Relatiue, an Art of Discypheringe; by supposition vnprofitable; but, as things are, of great vse. For suppose that Cyphars were well mannaged, there bee Multitudes of them which exclude the Discypherer. But in regarde of the rawnesse and Vnskilfulnesse of the handes, through which they passe, the greatest Matters, are many times carryed in the weakest CYPHARS. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 6 / 31
Secret writing in the past Francis Bacon 1605 Francis Bacon 1605 Of the Proficience and Advancement of Learning Divine and Humane Bacon’s three cryptographic principles that they be not laborious to write and read; User-friendly 1 that they be impossible to discipher; Secure 2 (in some cases) that they be without suspicion. 3 Hidden i.e. steganography No distinction between stego-systems and ciphers Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 6 / 31
Secret writing in the past Francis Bacon 1605 Francis Bacon 1605 Of the Proficience and Advancement of Learning Divine and Humane Bacon’s three cryptographic principles that they be not laborious to write and read; User-friendly 1 that they be impossible to discipher; Secure 2 (in some cases) that they be without suspicion. 3 Hidden i.e. steganography No distinction between stego-systems and ciphers Defined by purpose: keeping secrets. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 6 / 31
Secret writing in the past The Antique Outline Secret writing in the past 1 Francis Bacon 1605 The Antique Cryptography versus Steganography 2 Exercise 3 Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 7 / 31
Secret writing in the past The Antique Secret Writing in the Antique (Egypt) Tomb of Khnumethotep II c. 1900 B.C. Menet Khufu Rebuses obscure writing. Brain exercises – adds mystery same principles in Norse Runes (Orkneys and Scandinavia) (Mesopotamia) Seleucia 1500 B.C.: 3"x2" tablets Protect trade secrets. Earliest known formula for glazes for pottery. (India) K¯ ama-s¯ utra by V¯ atsy¯ ana (legendary erotics) 64 arts ( yogas ) women should know and practice mlecchita-vikalp¯ a (secret writing) is no. 45. (India) Artha´ s¯ astra 321-300BC but first political mention of cryptography Ambassadors should use cryptanalysis to gather intelligence. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 8 / 31
Secret writing in the past The Antique China: No cryptography Only great civilisation using ideogrammatic writing ... and only one with little interest in cryptography but steganograhy was used: Thin silk, covered in wax, rolled into balls (la wan) 11th century: Wu-ching tsung-yao (Essentials from Military Classics) List of 40 plaintext items (victory reports, requests for arrows, etc.) Assign to 40 first ideograms of a poem. Write appropriate ideogram in an ordinary dispatch, Mark by seal stamp over it. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 9 / 31
Secret writing in the past The Antique China: No cryptography Only great civilisation using ideogrammatic writing ... and only one with little interest in cryptography but steganograhy was used: Thin silk, covered in wax, rolled into balls (la wan) 11th century: Wu-ching tsung-yao (Essentials from Military Classics) List of 40 plaintext items (victory reports, requests for arrows, etc.) Assign to 40 first ideograms of a poem. Write appropriate ideogram in an ordinary dispatch, Mark by seal stamp over it. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 9 / 31
Secret writing in the past The Antique Elementary Steganography à la greque Reported in Histories by Herodotus (c. 486-425 B.C) Histæus 440 B.C. Shave the head of a slave 1 Tattoo the messages on his head 2 Wait until the hair grows back 3 Dispatch the Slave 4 (also used by Germany in the early 20th century) Wax tablets Remove the wax 1 Write the message on the wood 2 Recover with wax to make a blank tablet. 3 (Demeratus used it to warn Sparta of a Persian invasion) Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 10 / 31
Secret writing in the past The Antique Elementary Steganography à la greque Reported in Histories by Herodotus (c. 486-425 B.C) Histæus 440 B.C. Shave the head of a slave 1 Tattoo the messages on his head 2 Wait until the hair grows back 3 Dispatch the Slave 4 (also used by Germany in the early 20th century) Wax tablets Remove the wax 1 Write the message on the wood 2 Recover with wax to make a blank tablet. 3 (Demeratus used it to warn Sparta of a Persian invasion) Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 10 / 31
Secret writing in the past The Antique Elementary Steganography anno 18.. Pin holes in news papers Mark individual letters in a news paper make pin wholes overwrite with a pencil Invisible ink Quite a few methods Invisible to a casual observers Easy to spot when you know what to look for Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 11 / 31
Cryptography versus Steganography Outline Secret writing in the past 1 Cryptography versus Steganography 2 Kerckhoff’s principles Steganography versus Kerckhoffs Exercise 3 Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 12 / 31
Cryptography versus Steganography Kerckhoff’s principles Outline Secret writing in the past 1 Cryptography versus Steganography 2 Kerckhoff’s principles Steganography versus Kerckhoffs Exercise 3 Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 13 / 31
Cryptography versus Steganography Kerckhoff’s principles The Advent of Modern Cryptography Auguste Kerckhoff 1883 « La cryptographie militaire » Journal des sciences militaires 1883 Principles of military cryptography Defines the security paradigm Claude Shannon 1948 Defines Information ... and Entropy to measure Information quantitatively Enables mathematical proofs of security of information Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 14 / 31
Cryptography versus Steganography Kerckhoff’s principles The Advent of Modern Cryptography Auguste Kerckhoff 1883 « La cryptographie militaire » Journal des sciences militaires 1883 Principles of military cryptography Defines the security paradigm Claude Shannon 1948 Defines Information ... and Entropy to measure Information quantitatively Enables mathematical proofs of security of information Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 14 / 31
Cryptography versus Steganography Kerckhoff’s principles The Advent of Modern Cryptography Auguste Kerckhoff 1883 « La cryptographie militaire » Journal des sciences militaires 1883 Principles of military cryptography Defines the security paradigm Claude Shannon 1948 Defines Information ... and Entropy to measure Information quantitatively Enables mathematical proofs of security of information Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 14 / 31
Cryptography versus Steganography Kerckhoff’s principles The Advent of Modern Cryptography Auguste Kerckhoff 1883 « La cryptographie militaire » Journal des sciences militaires 1883 Principles of military cryptography Defines the security paradigm Claude Shannon 1948 Defines Information ... and Entropy to measure Information quantitatively Enables mathematical proofs of security of information Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 14 / 31
Cryptography versus Steganography Kerckhoff’s principles The Advent of Modern Cryptography Auguste Kerckhoff 1883 « La cryptographie militaire » Journal des sciences militaires 1883 Principles of military cryptography Defines the security paradigm Claude Shannon 1948 Defines Information ... and Entropy to measure Information quantitatively Enables mathematical proofs of security of information Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 14 / 31
Cryptography versus Steganography Kerckhoff’s principles The Advent of Modern Cryptography Auguste Kerckhoff 1883 « La cryptographie militaire » Journal des sciences militaires 1883 Principles of military cryptography Defines the security paradigm Claude Shannon 1948 Defines Information ... and Entropy to measure Information quantitatively Enables mathematical proofs of security of information Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 14 / 31
Cryptography versus Steganography Kerckhoff’s principles The Advent of Modern Cryptography Auguste Kerckhoff 1883 « La cryptographie militaire » Journal des sciences militaires 1883 Principles of military cryptography Defines the security paradigm Claude Shannon 1948 Defines Information ... and Entropy to measure Information quantitatively Enables mathematical proofs of security of information Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 14 / 31
Cryptography versus Steganography Kerckhoff’s principles Modern Cryptography Modern cryptography has mainly been shaped by Auguste Kerckhoff 1883 : The security paradigm Claude Shannon 1948 : Mathematical theory of information and Diffie & Hellman 1976 (Public Key Cryptography) The consequence of Modern day cryptography is Theoretically mature Reliable Highly trusted technology Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 15 / 31
Cryptography versus Steganography Kerckhoff’s principles Modern Cryptography Modern cryptography has mainly been shaped by Auguste Kerckhoff 1883 : The security paradigm Claude Shannon 1948 : Mathematical theory of information and Diffie & Hellman 1976 (Public Key Cryptography) The consequence of Modern day cryptography is Theoretically mature Reliable Highly trusted technology Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 15 / 31
Cryptography versus Steganography Kerckhoff’s principles Modern Cryptography Modern cryptography has mainly been shaped by Auguste Kerckhoff 1883 : The security paradigm Claude Shannon 1948 : Mathematical theory of information and Diffie & Hellman 1976 (Public Key Cryptography) The consequence of Modern day cryptography is Theoretically mature Reliable Highly trusted technology Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 15 / 31
Cryptography versus Steganography Kerckhoff’s principles Modern Cryptography Modern cryptography has mainly been shaped by Auguste Kerckhoff 1883 : The security paradigm Claude Shannon 1948 : Mathematical theory of information and Diffie & Hellman 1976 (Public Key Cryptography) The consequence of Modern day cryptography is Theoretically mature Reliable Highly trusted technology Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 15 / 31
Cryptography versus Steganography Kerckhoff’s principles Modern Cryptography Modern cryptography has mainly been shaped by Auguste Kerckhoff 1883 : The security paradigm Claude Shannon 1948 : Mathematical theory of information and Diffie & Hellman 1976 (Public Key Cryptography) The consequence of Modern day cryptography is Theoretically mature Reliable Highly trusted technology Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 15 / 31
Cryptography versus Steganography Kerckhoff’s principles Auguste Kerckhoffs (1835–1903) Le système doit être matériellement, sinon mathématiquement, 1 indéchiffrable ; Il faut qu’il n’exige pas le secret, et qu’il puisse sans inconvénient 2 tomber entre les mains de l’ennemi ; La clef doit pouvoir en être communiquée et retenue sans le 3 secours de notes écrites, et être changée ou modifiée au gré des correspondants ; Il faut qu’il soit applicable à la correspondance télégraphique ; 4 Il faut qu’il soit portatif, et que son maniement ou son 5 fonctionnement n’exige pas le concours de plusieurs personnes ; Enfin, il est nécessaire, vu les circonstances qui en commandent 6 l’application, que le système soit d’un usage facile, ne demandant ni tension d’esprit, ni la connaissance d’une longue série de règles à observer. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 16 / 31
Cryptography versus Steganography Kerckhoff’s principles Auguste Kerckhoffs (1835–1903) Translation from Wikipedia The system should be, if not theoretically unbreakable, unbreakable in practice. The design of a system should not require secrecy and compromise of the system should not inconvenience the correspondents The key should be rememberable without notes and should be easily changeable The cryptograms should be transmittable by telegraph The apparatus or documents should be portable and operable by a single person The system should be easy, neither requiring knowledge of a long list of rules nor involving mental strain Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 17 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s first principle User-friendliness Kerckhoffs says: 6. The system should be easy, neither requiring knowledge of a long list of rules nor involving mental strain Bacon said: that they be not laborious to write and reade Why? Security depends on correct use. If it is difficult, users make mistakes. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 18 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s first principle User-friendliness Kerckhoffs says: 6. The system should be easy, neither requiring knowledge of a long list of rules nor involving mental strain Bacon said: that they be not laborious to write and reade Why? Security depends on correct use. If it is difficult, users make mistakes. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 18 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s first principle User-friendliness Kerckhoffs says: 6. The system should be easy, neither requiring knowledge of a long list of rules nor involving mental strain Bacon said: that they be not laborious to write and reade Why? Security depends on correct use. If it is difficult, users make mistakes. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 18 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s first principle User-friendliness Kerckhoffs says: 6. The system should be easy, neither requiring knowledge of a long list of rules nor involving mental strain Bacon said: that they be not laborious to write and reade Why? Security depends on correct use. If it is difficult, users make mistakes. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 18 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s first principle User-friendliness Kerckhoffs says: 6. The system should be easy, neither requiring knowledge of a long list of rules nor involving mental strain Bacon said: that they be not laborious to write and reade Why? Security depends on correct use. If it is difficult, users make mistakes. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 18 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s first principle User-friendliness Kerckhoffs says: 6. The system should be easy, neither requiring knowledge of a long list of rules nor involving mental strain Kerckhoffs also says: 5. The apparatus or documents should be portable and oper- able by a single person Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 18 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s first principle User-friendliness Kerckhoffs says: 6. The system should be easy, neither requiring knowledge of a long list of rules nor involving mental strain Kerckhoffs also says: 5. The apparatus or documents should be portable and oper- able by a single person and 3. The key should be rememberable without notes and should be easily changeable Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 18 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s first principle User-friendliness Kerckhoffs says: 6. The system should be easy, neither requiring knowledge of a long list of rules nor involving mental strain Kerckhoffs also says: 5. The apparatus or documents should be portable and oper- able by a single person and 3. The key should be rememberable without notes and should be easily changeable (We will return to #3 in when we discuss keys.) Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 18 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s second principle Security Kerckhoffs says: The system should be, if not theoretically unbreakable, unbreakable in practice. Bacon said: that they bee impossible to discypher Security still essential. Bacon did not clarify the meaning of «impossible». Kerckhoffs allows theoretically breakable ciphers. Why? Are theoretically unbreakable cipers at all possible? Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 19 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s second principle Security Kerckhoffs says: The system should be, if not theoretically unbreakable, unbreakable in practice. Bacon said: that they bee impossible to discypher Security still essential. Bacon did not clarify the meaning of «impossible». Kerckhoffs allows theoretically breakable ciphers. Why? Are theoretically unbreakable cipers at all possible? Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 19 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s second principle Security Kerckhoffs says: The system should be, if not theoretically unbreakable, unbreakable in practice. Bacon said: that they bee impossible to discypher Security still essential. Bacon did not clarify the meaning of «impossible». Kerckhoffs allows theoretically breakable ciphers. Why? Are theoretically unbreakable cipers at all possible? Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 19 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s second principle Security Kerckhoffs says: The system should be, if not theoretically unbreakable, unbreakable in practice. Bacon said: that they bee impossible to discypher Security still essential. Bacon did not clarify the meaning of «impossible». Kerckhoffs allows theoretically breakable ciphers. Why? Are theoretically unbreakable cipers at all possible? Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 19 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s second principle Security Kerckhoffs says: The system should be, if not theoretically unbreakable, unbreakable in practice. Bacon said: that they bee impossible to discypher Security still essential. Bacon did not clarify the meaning of «impossible». Kerckhoffs allows theoretically breakable ciphers. Why? Are theoretically unbreakable cipers at all possible? Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 19 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s second principle Security Kerckhoffs says: The system should be, if not theoretically unbreakable, unbreakable in practice. Bacon said: that they bee impossible to discypher Security still essential. Bacon did not clarify the meaning of «impossible». Kerckhoffs allows theoretically breakable ciphers. Why? Are theoretically unbreakable cipers at all possible? Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 19 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s second principle Security Kerckhoffs says: The system should be, if not theoretically unbreakable, unbreakable in practice. Bacon said: that they bee impossible to discypher Security still essential. Bacon did not clarify the meaning of «impossible». Kerckhoffs allows theoretically breakable ciphers. Why? Are theoretically unbreakable cipers at all possible? Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 19 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s second principle Security Kerckhoffs says: The system should be, if not theoretically unbreakable, unbreakable in practice. Bacon said: that they bee impossible to discypher Security still essential. Bacon did not clarify the meaning of «impossible». Kerckhoffs allows theoretically breakable ciphers. Why? Are theoretically unbreakable cipers at all possible? Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 19 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s third principle Steganography Bacon said: that they bee without suspition. Not mentioned by Kerckhoffs. Why not? He addressed military communications. You already know who the enemies are. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 20 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s third principle Steganography Bacon said: that they bee without suspition. Not mentioned by Kerckhoffs. Why not? He addressed military communications. You already know who the enemies are. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 20 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s third principle Steganography Bacon said: that they bee without suspition. Not mentioned by Kerckhoffs. Why not? He addressed military communications. You already know who the enemies are. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 20 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s third principle Steganography Bacon said: that they bee without suspition. Not mentioned by Kerckhoffs. Why not? He addressed military communications. You already know who the enemies are. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 20 / 31
Cryptography versus Steganography Kerckhoff’s principles Bacon’s third principle Steganography Bacon said: that they bee without suspition. Not mentioned by Kerckhoffs. Why not? He addressed military communications. You already know who the enemies are. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 20 / 31
Cryptography versus Steganography Kerckhoff’s principles Kerckhoffs’ fourth principle Telegraph «The cryptograms should be transmittable by telegraph.» Why does he require this? What do we require today? Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 21 / 31
Cryptography versus Steganography Kerckhoff’s principles Kerckhoffs’ fourth principle Telegraph «The cryptograms should be transmittable by telegraph.» Why does he require this? What do we require today? Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 21 / 31
Cryptography versus Steganography Kerckhoff’s principles Kerckhoffs’ fourth principle Telegraph «The cryptograms should be transmittable by telegraph.» Why does he require this? What do we require today? Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 21 / 31
Cryptography versus Steganography Kerckhoff’s principles Kerckhoffs’ principle The key principle 2. The design of a system should not require secrecy and compromise of the system should not inconvenience the correspondents This is the one known as Kerckhoffs’ principle. Foundation of all modern cryptography. All modern cryptographic algorithms are published in detail. Available to Eve as well as Alice and Bob. How is secrecy possible? Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 22 / 31
Cryptography versus Steganography Kerckhoff’s principles Kerckhoffs’ principle The key principle 2. The design of a system should not require secrecy and compromise of the system should not inconvenience the correspondents This is the one known as Kerckhoffs’ principle. Foundation of all modern cryptography. All modern cryptographic algorithms are published in detail. Available to Eve as well as Alice and Bob. How is secrecy possible? Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 22 / 31
Cryptography versus Steganography Kerckhoff’s principles Kerckhoffs’ principle The key principle 2. The design of a system should not require secrecy and compromise of the system should not inconvenience the correspondents This is the one known as Kerckhoffs’ principle. Foundation of all modern cryptography. All modern cryptographic algorithms are published in detail. Available to Eve as well as Alice and Bob. How is secrecy possible? Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 22 / 31
Cryptography versus Steganography Kerckhoff’s principles Kerckhoffs’ principle The key principle 2. The design of a system should not require secrecy and compromise of the system should not inconvenience the correspondents This is the one known as Kerckhoffs’ principle. Foundation of all modern cryptography. All modern cryptographic algorithms are published in detail. Available to Eve as well as Alice and Bob. How is secrecy possible? Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 22 / 31
Cryptography versus Steganography Kerckhoff’s principles Kerckhoffs’ principle The key principle 2. The design of a system should not require secrecy and compromise of the system should not inconvenience the correspondents This is the one known as Kerckhoffs’ principle. Foundation of all modern cryptography. All modern cryptographic algorithms are published in detail. Available to Eve as well as Alice and Bob. How is secrecy possible? Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 22 / 31
Cryptography versus Steganography Kerckhoff’s principles The key The use of a key is crucial for Kerckhoffs’ principle. 3. The key should be rememberable without notes and should be easily changeable. So, we have Public algorithm Difficult (expensive) to develop few good choices Secret key Easy (cheap) to change Many possibilities Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 23 / 31
Cryptography versus Steganography Kerckhoff’s principles The key The use of a key is crucial for Kerckhoffs’ principle. 3. The key should be rememberable without notes and should be easily changeable. So, we have Public algorithm Difficult (expensive) to develop few good choices Secret key Easy (cheap) to change Many possibilities Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 23 / 31
Cryptography versus Steganography Kerckhoff’s principles The key The use of a key is crucial for Kerckhoffs’ principle. 3. The key should be rememberable without notes and should be easily changeable. So, we have Public algorithm Difficult (expensive) to develop few good choices Secret key Easy (cheap) to change Many possibilities Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 23 / 31
Cryptography versus Steganography Kerckhoff’s principles The key The use of a key is crucial for Kerckhoffs’ principle. 3. The key should be rememberable without notes and should be easily changeable. So, we have Public algorithm Difficult (expensive) to develop few good choices Secret key Easy (cheap) to change Many possibilities Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 23 / 31
Cryptography versus Steganography Kerckhoff’s principles The key The use of a key is crucial for Kerckhoffs’ principle. 3. The key should be rememberable without notes and should be easily changeable. So, we have Public algorithm Difficult (expensive) to develop few good choices Secret key Easy (cheap) to change Many possibilities Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 23 / 31
Cryptography versus Steganography Kerckhoff’s principles Consequences We need not trust the developers. The key can be changed by the user Security assessment by independent experts. Mass-produced crypto-software off the shelf. Eve buys the same software; it does not matter. No new costly development is required when secrets are lost Changing the key is easy (cheap) All new crypto-systems are published in detail scrutinised by independent researchers world-wide Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 24 / 31
Cryptography versus Steganography Kerckhoff’s principles Consequences We need not trust the developers. The key can be changed by the user Security assessment by independent experts. Mass-produced crypto-software off the shelf. Eve buys the same software; it does not matter. No new costly development is required when secrets are lost Changing the key is easy (cheap) All new crypto-systems are published in detail scrutinised by independent researchers world-wide Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 24 / 31
Cryptography versus Steganography Kerckhoff’s principles Consequences We need not trust the developers. The key can be changed by the user Security assessment by independent experts. Mass-produced crypto-software off the shelf. Eve buys the same software; it does not matter. No new costly development is required when secrets are lost Changing the key is easy (cheap) All new crypto-systems are published in detail scrutinised by independent researchers world-wide Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 24 / 31
Cryptography versus Steganography Kerckhoff’s principles Consequences We need not trust the developers. The key can be changed by the user Security assessment by independent experts. Mass-produced crypto-software off the shelf. Eve buys the same software; it does not matter. No new costly development is required when secrets are lost Changing the key is easy (cheap) All new crypto-systems are published in detail scrutinised by independent researchers world-wide Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 24 / 31
Cryptography versus Steganography Kerckhoff’s principles Consequences We need not trust the developers. The key can be changed by the user Security assessment by independent experts. Mass-produced crypto-software off the shelf. Eve buys the same software; it does not matter. No new costly development is required when secrets are lost Changing the key is easy (cheap) All new crypto-systems are published in detail scrutinised by independent researchers world-wide Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 24 / 31
Cryptography versus Steganography Kerckhoff’s principles Consequences We need not trust the developers. The key can be changed by the user Security assessment by independent experts. Mass-produced crypto-software off the shelf. Eve buys the same software; it does not matter. No new costly development is required when secrets are lost Changing the key is easy (cheap) All new crypto-systems are published in detail scrutinised by independent researchers world-wide Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 24 / 31
Cryptography versus Steganography Kerckhoff’s principles Consequences We need not trust the developers. The key can be changed by the user Security assessment by independent experts. Mass-produced crypto-software off the shelf. Eve buys the same software; it does not matter. No new costly development is required when secrets are lost Changing the key is easy (cheap) All new crypto-systems are published in detail scrutinised by independent researchers world-wide Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 24 / 31
Cryptography versus Steganography Kerckhoff’s principles Consequences We need not trust the developers. The key can be changed by the user Security assessment by independent experts. Mass-produced crypto-software off the shelf. Eve buys the same software; it does not matter. No new costly development is required when secrets are lost Changing the key is easy (cheap) All new crypto-systems are published in detail scrutinised by independent researchers world-wide Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 24 / 31
Cryptography versus Steganography Kerckhoff’s principles Consequences We need not trust the developers. The key can be changed by the user Security assessment by independent experts. Mass-produced crypto-software off the shelf. Eve buys the same software; it does not matter. No new costly development is required when secrets are lost Changing the key is easy (cheap) All new crypto-systems are published in detail scrutinised by independent researchers world-wide Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 24 / 31
Cryptography versus Steganography Kerckhoff’s principles Consequences We need not trust the developers. The key can be changed by the user Security assessment by independent experts. Mass-produced crypto-software off the shelf. Eve buys the same software; it does not matter. No new costly development is required when secrets are lost Changing the key is easy (cheap) All new crypto-systems are published in detail scrutinised by independent researchers world-wide Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 24 / 31
Cryptography versus Steganography Kerckhoff’s principles Summary Kerckhoffs’ Principles in Four Keywords User-friendly Secure in practice (not necessarily in theory) Public algorithm – secret key Telegraph Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 25 / 31
Cryptography versus Steganography Steganography versus Kerckhoffs Outline Secret writing in the past 1 Cryptography versus Steganography 2 Kerckhoff’s principles Steganography versus Kerckhoffs Exercise 3 Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 26 / 31
Cryptography versus Steganography Steganography versus Kerckhoffs Kerckhooffs’ principle and classic steganography Recall tattooed slaves and wax tablets How does Kerckhoffs’ principle apply? It worked once – because it was unexpected Now the technique is known. Eve is going to shave all slaves passing by. ... and scrutinise every wax tablet. No key : when the algorithm is known there is no security Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 27 / 31
Cryptography versus Steganography Steganography versus Kerckhoffs Kerckhooffs’ principle and classic steganography Recall tattooed slaves and wax tablets How does Kerckhoffs’ principle apply? It worked once – because it was unexpected Now the technique is known. Eve is going to shave all slaves passing by. ... and scrutinise every wax tablet. No key : when the algorithm is known there is no security Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 27 / 31
Cryptography versus Steganography Steganography versus Kerckhoffs Kerckhooffs’ principle and classic steganography Recall tattooed slaves and wax tablets How does Kerckhoffs’ principle apply? It worked once – because it was unexpected Now the technique is known. Eve is going to shave all slaves passing by. ... and scrutinise every wax tablet. No key : when the algorithm is known there is no security Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 27 / 31
Cryptography versus Steganography Steganography versus Kerckhoffs What about modern steganography? Many computer programs became available during the 90-s. Many free of charge. Hiding messages in images. For instance, using Least Significant Bit (LSB) Most are as banale as the ancient techniques. It is relatively easy to detect the changes, you only have to think of it. Many solutions rely on the secrecy of the algorithm I.e. not Kerckhoffs-compliant Not Modern Cryptography. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 28 / 31
Cryptography versus Steganography Steganography versus Kerckhoffs What about modern steganography? Many computer programs became available during the 90-s. Many free of charge. Hiding messages in images. For instance, using Least Significant Bit (LSB) Most are as banale as the ancient techniques. It is relatively easy to detect the changes, you only have to think of it. Many solutions rely on the secrecy of the algorithm I.e. not Kerckhoffs-compliant Not Modern Cryptography. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 28 / 31
Cryptography versus Steganography Steganography versus Kerckhoffs What about modern steganography? Many computer programs became available during the 90-s. Many free of charge. Hiding messages in images. For instance, using Least Significant Bit (LSB) Most are as banale as the ancient techniques. It is relatively easy to detect the changes, you only have to think of it. Many solutions rely on the secrecy of the algorithm I.e. not Kerckhoffs-compliant Not Modern Cryptography. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 28 / 31
Cryptography versus Steganography Steganography versus Kerckhoffs What about modern steganography? Many computer programs became available during the 90-s. Many free of charge. Hiding messages in images. For instance, using Least Significant Bit (LSB) Most are as banale as the ancient techniques. It is relatively easy to detect the changes, you only have to think of it. Many solutions rely on the secrecy of the algorithm I.e. not Kerckhoffs-compliant Not Modern Cryptography. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 28 / 31
Cryptography versus Steganography Steganography versus Kerckhoffs What about modern steganography? Many computer programs became available during the 90-s. Many free of charge. Hiding messages in images. For instance, using Least Significant Bit (LSB) Most are as banale as the ancient techniques. It is relatively easy to detect the changes, you only have to think of it. Many solutions rely on the secrecy of the algorithm I.e. not Kerckhoffs-compliant Not Modern Cryptography. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 28 / 31
Cryptography versus Steganography Steganography versus Kerckhoffs What about modern steganography? Many computer programs became available during the 90-s. Many free of charge. Hiding messages in images. For instance, using Least Significant Bit (LSB) Most are as banale as the ancient techniques. It is relatively easy to detect the changes, you only have to think of it. Many solutions rely on the secrecy of the algorithm I.e. not Kerckhoffs-compliant Not Modern Cryptography. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 28 / 31
Cryptography versus Steganography Steganography versus Kerckhoffs What about modern steganography? Many computer programs became available during the 90-s. Many free of charge. Hiding messages in images. For instance, using Least Significant Bit (LSB) Most are as banale as the ancient techniques. It is relatively easy to detect the changes, you only have to think of it. Many solutions rely on the secrecy of the algorithm I.e. not Kerckhoffs-compliant Not Modern Cryptography. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 28 / 31
Cryptography versus Steganography Steganography versus Kerckhoffs What about modern steganography? Many computer programs became available during the 90-s. Many free of charge. Hiding messages in images. For instance, using Least Significant Bit (LSB) Most are as banale as the ancient techniques. It is relatively easy to detect the changes, you only have to think of it. Many solutions rely on the secrecy of the algorithm I.e. not Kerckhoffs-compliant Not Modern Cryptography. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 28 / 31
Cryptography versus Steganography Steganography versus Kerckhoffs What about modern steganography? Many computer programs became available during the 90-s. Many free of charge. Hiding messages in images. For instance, using Least Significant Bit (LSB) Most are as banale as the ancient techniques. It is relatively easy to detect the changes, you only have to think of it. Many solutions rely on the secrecy of the algorithm I.e. not Kerckhoffs-compliant Not Modern Cryptography. Dr Hans Georg Schaathun History and Principles of Steganography Spring 2009 – Week 6 28 / 31
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