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Title: Fea-m  
Author: World Heritage Encyclopedia
Language: English
Subject: Cobra ciphers, Xor-encrypt-xor, Lai-Massey scheme, BEAR and LION ciphers, Chiasmus (cipher)
Publisher: World Heritage Encyclopedia


Designers X. Yi, C.H. Tan, C.K. Siew, and M.R. Syed
First published 2001
Cipher detail
Key sizes about 4094.2 bits
Block sizes 4096 bits
Rounds 1
Best public cryptanalysis
Youssef and Tavares break it with 1 known plaintext and 2 chosen plaintexts

In cryptography, FEA-M (Fast Encryption Algorithm for Multimedia) is a block cipher developed in 2001 by X. Yi, C. H. Tan, C. K. Siew, and M. R. Syed.

With the unusually large block size of 4096 bits, all of FEA-M's calculations operate on 64×64 binary matrices. Unlike most block ciphers, FEA-M does not use multiple rounds of encryption. Each block is encrypted using just two multiplications and two additions. The data is encrypted using a pair of session keys chosen for just that message. The key is an invertible matrix used to encrypt the session keys, and the encrypted session keys must be sent along with the ciphertext. Since only invertible matrices can be used for the key, the effective key size is about 4094.2 bits.

FEA-M is insecure; an attack found by Youssef and Tavares (2003) recovers the secret key using only 1 known plaintext and 2 chosen plaintexts.[1]


  • Hongjun Wu, Feng Bao, and Robert H. Deng (October 2003). "An Efficient Known Plaintext Attack on FEA-M" ( 
  1. ^ Li, Shujun; Lo, Kwok-Tung (14 June 2006). "Security problems with improper implementations of improved FEA-M". Journal of Systems and Software 80 (5): 791–794.  

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