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There is absolutely no reason to use HMAC-MD5 in a new product. Don't. HMAC-MD5 security can still work in many roles, but should not be regarded as "secure" unless you can do extensive analysis as to EXACTLY how it's used. In particular, it is "secure" for document signing only if you are sure that the signer is NOT motivated to break security. What ...


1

So first we'll assume the end-game is to perform a dictionary attack on the not-yet-known hash. In that case you also have a dictionary. First, store the dictionary it's md5 hashes in a database, with a sort index on the md5 hashes. Now, for each character of the hash: Select an md5 hash starting with what you know so far plus 1 extra character for each ...


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There is no timing attack possible on MD5 as practically implemented on most platforms. That's because MD5 uses only 32-bit addition, 32-bit bitwise boolean operators, and constant rotations/shifts, which exhibit no data-dependent timing for any reasonable implementation, even written without consideration for resistance to timing attacks. There is however ...


6

Summary: a single HMAC-MD5 with a key later revealed is a completely insecure way to do commitments of messages that can be chosen malignantly, because of the ease with which MD5 collisions can now be found. There is no compelling evidence that's so insecure for messages constrained to belong in a small arbitrary set that no adversary can choose or ...



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