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SEED
- For other meanings of seed, see seed (disambiguation).
SEED is a block cipher developed by the Korean Information Security Agency. It is used broadly throughout South Korean industry, but seldom found elsewhere.
SEED is a 16-round Feistel network with 128-bit blocks and a 128-bit key. It uses two 8 × 8 S-boxes which, like those of SAFER, are derived from discrete exponentiation (in this case, x247 and x251 – plus some "incompatible operations"). It also has some resemblance to MISTY1 in the recursiveness of its structure: the 128-bit full cipher is a Feistel network with an F-function operating on 64-bit halves, while the F-function itself is a Feistel network composed of a G-function operating on 32-bit halves. However the recursion does not extend further because the G-function is not a Feistel network. In the G-function, the 32-bit word is considered as four 8-bit bytes, each of which is passed through one or the other of the S-boxes, then combined in a moderately complex set of boolean functions such that each output bit depends on 3 of the 4 input bytes.
SEED has a fairly complex key schedule, generating its thirty-two 32-bit subkeys through application of its G-function on a series of rotations of the raw key, combined with round constants derived (as in TEA) from the Golden ratio.
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