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Jan
28
comment Why does Skein use an output transform, but other similar hashes don't?
You do not need any output transformation at all. :-) In the case of SKEIN, the authors claim the following: "Originally we applied the output transformation only if the output size was larger than the state size. Unfortunately, without the output transform, you can construct two messages M and M' such that H(M) xor H(M) is the same as the XOR of the last blocks of M and M . (A similar property has recently been described for SHA-1 [101].) This violates the requirement that the hash function behave like a random mapping." -- The Skein Hash Function Family, Version 1.3.
Jan
28
answered Is there a length-preserving encryption scheme?
Oct
24
answered Can I use guids / uuids as counters for key derivation?
Oct
22
awarded  Supporter
Oct
22
revised Why does Skein use an output transform, but other similar hashes don't?
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Oct
22
answered Why does Skein use an output transform, but other similar hashes don't?
Oct
22
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Oct
22
revised Is AES-256 weaker than 192 and 128 bit versions?
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Oct
21
answered Is AES-256 weaker than 192 and 128 bit versions?
Oct
5
awarded  Teacher
Oct
2
answered Is 512-bit RSA still safe for signature generation?