Single-block collision for MD5

Re:Single-block collision for MD5 by bdonlan on Sunday January 29, 2012 @02:16PM (#3525868)

It is. The MD5 preimage attacks support arbitrary (non-common) prefixes and arbitrary common suffixes. With complex file format like a word document, it's easy enough to put a binary blob at the end of the file that doesn't affect how it looks to the user, and the content before that point can be whatever you want (as long as it's the same binary length, which is also easy enough to arrange).

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Re:Single-block collision for MD5 by mrb on Monday January 30, 2012 @03:12PM (#3530452)

There are no known "preimage attacks" against MD5. Only collision attacks. The term you are looking for is a "chosen prefix collision attack".

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Re:Single-block collision for MD5 by pronoiac on Sunday January 29, 2012 @08:25PM (#3527041)

Huh. I hadn't known about the MD5 preimage attacks. I'd planned to use salted MD5 to generate nonces, possibly with HMAC. How unsafe is that?

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Re:Single-block collision for MD5 by jakejake on Monday January 30, 2012 @02:55PM (#3530366)

that's pretty interesting, i had assumed that it would be fairly easy to create duplicate content with the same signature, but nearly impossible to make that content something usable.

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