How Does Mallory Pass Encrypted Data Without Bob Detecting It?

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Mallory and Eve are being watched by Bob the Investigator. They must now try and pass messages to each other, with Bob detecting the passing of secret messages.

If Mallory wants to trick Bob the Investigator into thinking that he is sending plain text, then he can covert the cipher text into a plain text format. In the following Mallory converts the cipher text using RFC 1751 [here]:

This converts 11 bits values to a word (where there are 2¹¹ words) [here]:

Input data (CMS): 48656c6c6f20686f772061726520796f750f0f0f0f0f0f0f0f0f0f0f0f0f0f0fCipher (ECB): c10c2fc11e3d73e1bc74b836b9cc8698deeae276ede8eb5a19d4f4405fda42e1Cipher to plain: MUTT BUSS TRUE SIS SAVE TUCK MIRE KENO DEE DINT OMIT AMMO SLID BETA HYMN SIGH GOOD LENT HEM KNIT DUE MOVE JUNK DEAFReverse: 2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824decrypt: Hello how are you

If this case we use CMS padding, and where we pad with a value that fills up to 16 bytes (128 bit block size). Here are the starting point of the 2,048…

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Prof Bill Buchanan OBE FRSE
ASecuritySite: When Bob Met Alice

Professor of Cryptography. Serial innovator. Believer in fairness, justice & freedom. Based in Edinburgh. Old World Breaker. New World Creator. Building trust.