Feistel Model Last Updated: Aug 27, 2013. Feistel Cipher Structure Described by Horst Feistel (IBM) in 1973 Many symmetric encryption algorithms use this.

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Feistel Model Last Updated: Aug 27, 2013

Feistel Cipher Structure Described by Horst Feistel (IBM) in 1973 Many symmetric encryption algorithms use this structure o DES, IDEA, Blowfish, RC6, MARS, Twofish o Not AES Substitution-permutation network Block cipher Features – block size, key size, number of rounds, sub-key generation algorithm, round function Decryption is essentially the same as encryption o Input: ciphertext o Use sub-keys in reverse order Sources o Stallings NSE Fig 2.2 (next slide) o Wikipedie: Feistel Cipher

Source: Network Security Essentials (Stallings)

The Feistel Network Round Function (F) The Feistel network is guaranteed to be reversible if we can reconstruct its inputs, which are derived from the key It doesn’t matter how complicated or simple F is or if it can be inverted

Proof of Feistel Network On the board What is the disadvantage of a 1-round Feistel network?