# Re: Could anyone verify a term for me?

*From*: BRG <brg@xxxxxxxxxxx>*Date*: Tue, 13 Jun 2006 09:43:43 +0100

William L. Bahn wrote:

"Hipo" <no@xxxxxxxxx> wrote in message

news:448dbf8e$0$11094$3b214f66@xxxxxxxxxxxxxxxxxxxxxxx

Hi.two days

I'm coding a SHA-1 implementation and I'm stuck at a point for

now. I have to compute:(~0xefcdab89 &

T = _rotl(0x67452301, 5) + ((0xefcdab89 & 0x98badcfe) xor

0x10325476)) + 0xc3d2e1f0 + 0x5a827999 + 0x80636261;result for T

All numbers are unsigned ints and therfor 2^32 bit long. My

is always 0x2017fb14, but the partial result of a testvectorin the

standard paper claims T to be 0x0116fc33.the

Could please anyone verify my result? It's driving me nuts and

algorithm is almost due.

thanks in advance, Hipo

I get the same result you do.

You didn't provide enough info to really know where in the hash

algorithm you are working, so I'm having to reverse engineer

where you are at. Initially, at least, I'm going to assume you

are at the very first pass through the main loop.

(snippets of algorithm taken from Wikipedia)

http://en.wikipedia.org/wiki/SHA1

a = 0x67452301

b = 0xEFCDAB89

c = 0x98BADCFE

d = 0x10325476

e = 0xC3D2E1F0

f = (b & c) | ((~b) & d) // notice inclusive-OR

k = 0x5A827999

Substituting into your expression:

T = _rotl(0x67452301, 5) + ((0xefcdab89 & 0x98badcfe) xor(~0xefcdab89 &

0x10325476)) + 0xc3d2e1f0 + 0x5a827999 + 0x80636261;

becomes

T = _rotl(a, 5) + [((b & c) xor ((~b) & d))] + e + k +0x80636261;

Now, the last term comes from the message being hashed, so I have

no idea where it is coming from in this particular case and

whether or not you have it correct.

[snip]

0x80636261 is what the ascii string "abc" becomes with a 0x80 terminator

in little endian notation in a 32-bit word.

But SHA-1 requires that its input data is in big-endian form within

32-bit words, in this case as W[0] = 0x61626380.

So the original poster's problem is pretty certain to be that they have

not put the input data into the correct big-endian format.

Brian Gladman

.

**References**:**Could anyone verify a term for me?***From:*Hipo

**Re: Could anyone verify a term for me?***From:*William L. Bahn

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