is sha1( secret + m') possible from sha1(secret + m) where m is public
in [Cryptography]
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From: mar on 17 Feb 2010 20:48 I know that sha1(secret + m) is insecure construction and it may be possible to construct sha1(secret + m + m') without knowing secret. However, is it possible to compute sha1(secret + m') without knowing secret where m' may contain some bits from m, if m is known by inverting the operations of SHA1. If this is possible, then under what conditions? such as should length of secret be known or m has to be at least 1 block size, etc. Thanks.
From: Greg Rose on 18 Feb 2010 12:53
In article <8da37fa1-05c8-4dbf-804c-fd73dea1fed8(a)x1g2000prb.googlegroups.com>, mar <marvind434(a)gmail.com> wrote: >I know that sha1(secret + m) is insecure construction and it may be >possible to construct sha1(secret + m + m') without knowing secret. >However, is it possible to compute sha1(secret + m') without knowing >secret where m' may contain some bits from m, if m is known by >inverting the operations of SHA1. If this is possible, then under what >conditions? such as should length of secret be known or m has to be at >least 1 block size, etc. I think the answer is no, but it might be yes except that we don't know how. At least we know it is computationally intractable but possible. I think. Greg. -- Greg Rose 232B EC8F 44C6 C853 D68F E107 E6BF CD2F 1081 A37C |