Cryptanalysis is the discipline of deciphering a ciphertext without having access to the keytext (see cryptosystem), usually by recovering more or less directly the plaintext or even the keytext used, in cases favorable for the attacker by reconstructing the whole cryptosystem used. This being the worst case possible for the attacked side, an acceptable level of security should rest completely in the key (see Kerckhoffs' and Shannon's maximes). “A systematic and exact reconstruction of the encryption method and the key used” (Hans Rohrbach, 1946) is mandatory if correctness of a cryptanalytic break is a to be proved, e.g., when a cryptanalyst is a witness to the prosecution.
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Cryptanalysis can be passive, which is the classical case of intercepting the message without giving any hint that this was done, or active, which consists of altering the message or retransmitting it at a later time, or even of inserting own messages (some of these actions may be detected by the...
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References
Bauer, F.L. (1997). “Decrypted secrets.” Methods and Maxims of Cryptology. Springer-Verlag, Berlin.
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© 2005 International Federation for Information Processing
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Bauer, F.L. (2005). Cryptanalysis. In: van Tilborg, H.C.A. (eds) Encyclopedia of Cryptography and Security. Springer, Boston, MA . https://doi.org/10.1007/0-387-23483-7_87
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