Russian copulation
Encyclopedia
In cryptography
, Russian copulation is a method of rearranging plaintext
before encryption
so as to conceal stereotyped headers, salutations, introductions, endings, signatures, etc. This obscures clues for a cryptanalyst, and can be used to increase cryptanalytic difficulty in naive cryptographic schemes (however, most modern schemes contain more rigorous defences; see Ciphertext indistinguishability
). This is of course desirable for those sending messages and wishing them to remain confidential. Padding
is another technique for obscuring such clues.
The technique is to break the starting plaintext message into two parts and then to invert the order of the parts. This puts all endings and beginnings (presumably the location of most boilerplate
phrases) 'somewhere in the middle' of the version of the plaintext which is actually encrypted. For some messages, mostly those not in a human language (e.g., images or tabular data), the decrypted version of the plaintext will present problems when reversing the inversion. For messages in ordinary language, there is sufficient redundancy that the inversion can almost always be reversed by a human immediately on inspection.
The English phrase suggests that it originally came from an observation about Russian cryptographic practice. However, the technique is generally useful and neither was, nor is, limited to use by Russians.
Cryptography
Cryptography is the practice and study of techniques for secure communication in the presence of third parties...
, Russian copulation is a method of rearranging plaintext
Plaintext
In cryptography, plaintext is information a sender wishes to transmit to a receiver. Cleartext is often used as a synonym. Before the computer era, plaintext most commonly meant message text in the language of the communicating parties....
before encryption
Encryption
In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...
so as to conceal stereotyped headers, salutations, introductions, endings, signatures, etc. This obscures clues for a cryptanalyst, and can be used to increase cryptanalytic difficulty in naive cryptographic schemes (however, most modern schemes contain more rigorous defences; see Ciphertext indistinguishability
Ciphertext indistinguishability
Ciphertext indistinguishability is a property of many encryption schemes. Intuitively, if a cryptosystem possesses the property of indistinguishability, then an adversary will be unable to distinguish pairs of ciphertexts based on the message they encrypt...
). This is of course desirable for those sending messages and wishing them to remain confidential. Padding
Padding (cryptography)
-Classical cryptography:Official messages often start and end in predictable ways: My dear ambassador, Weather report, Sincerely yours, etc. The primary use of padding with classical ciphers is to prevent the cryptanalyst from using that predictability to find cribs that aid in breaking the...
is another technique for obscuring such clues.
The technique is to break the starting plaintext message into two parts and then to invert the order of the parts. This puts all endings and beginnings (presumably the location of most boilerplate
Boilerplate (text)
Boilerplate is any text that is or can be reused in new contexts or applications without being changed much from the original. Many computer programmers often use the term boilerplate code. A legal boilerplate is a standard provision in a contract....
phrases) 'somewhere in the middle' of the version of the plaintext which is actually encrypted. For some messages, mostly those not in a human language (e.g., images or tabular data), the decrypted version of the plaintext will present problems when reversing the inversion. For messages in ordinary language, there is sufficient redundancy that the inversion can almost always be reversed by a human immediately on inspection.
The English phrase suggests that it originally came from an observation about Russian cryptographic practice. However, the technique is generally useful and neither was, nor is, limited to use by Russians.