{
  "id": "enwiki-001372141789",
  "slug": "m6-cipher",
  "title": "M6 (cipher)",
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  "lead": "In cryptography, M6 is a block cipher proposed by Hitachi in 1997 for use in the IEEE 1394 FireWire standard. The design allows some freedom in choosing a few of the cipher's operations, so M6 is considered a family of ciphers. Due to export controls, M6 has not been fully published; nevertheless, a partial description of the algorithm based on a draft standard is given by Kelsey, et al. in their cryptanalysis of this family of ciphers. The algorithm operates on blocks of 64 bits using a 10-round Feistel network structure. The key size is 40 bits by default, but can be up to 64 bits. The key schedule is very simple, producing two 32-bit subkeys: the high 32 bits of the key, and the sum mod 2 32 of this and the low 32 bits. Because its round function is based on rotation and addition, M6 was one of the first ciphers attacked by mod n cryptanalysis. Mod 5, about 100 known plaintexts suffice to distinguish the output from a pseudorandom permutation. Mod 257, information about the secret key itself is revealed. One known plaintext reduces the complexity of a brute force attack to about 2 35 trial encryptions; \"a few dozen\" known plaintexts lowers this number to about 2 31 . Due to its simple key schedule, M6 is also vulnerable to a slide attack, which requires more known plaintext but less computation.",
  "body": "In cryptography, M6 is a block cipher proposed by Hitachi in 1997 for use in the IEEE 1394 FireWire standard. The design allows some freedom in choosing a few of the cipher's operations, so M6 is considered a family of ciphers. Due to export controls, M6 has not been fully published; nevertheless, a partial description of the algorithm based on a draft standard is given by Kelsey, et al. in their cryptanalysis of this family of ciphers. The algorithm operates on blocks of 64 bits using a 10-round Feistel network structure. The key size is 40 bits by default, but can be up to 64 bits. The key schedule is very simple, producing two 32-bit subkeys: the high 32 bits of the key, and the sum mod 2 32 of this and the low 32 bits. Because its round function is based on rotation and addition, M6 was one of the first ciphers attacked by mod n cryptanalysis. Mod 5, about 100 known plaintexts suffice to distinguish the output from a pseudorandom permutation. Mod 257, information about the secret key itself is revealed. One known plaintext reduces the complexity of a brute force attack to about 2 35 trial encryptions; \"a few dozen\" known plaintexts lowers this number to about 2 31 . Due to its simple key schedule, M6 is also vulnerable to a slide attack, which requires more known plaintext but less computation. ==References==",
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    "title": "M6 (cipher)",
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    "publisher": "Anticloud FZ LLE",
    "publisher-place": "Dubai, United Arab Emirates",
    "URL": "https://encyclopegia.org/a/m6-cipher",
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          2026,
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          15
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