Take the 2-minute tour ×
Cryptography Stack Exchange is a question and answer site for software developers, mathematicians and others interested in cryptography. It's 100% free, no registration required.

I am implementing an ECDSA NIST test vectors verification application. The test vectors are taken from http://csrc.nist.gov/groups/STM/cavp/#09.

One of the test vectors is given below:

P-192 SHA1

Msg = 608079423f12421de616b7493ebe551cf4d65b92   
d = e14f37b3d1374ff8b03f41b9b3fdd2f0ebccf275d660d7f3   
Qx = 07008ea40b08dbe76432096e80a2494c94982d2d5bcf98e6     
Qy = 76fab681d00b414ea636ba215de26d98c41bd7f2e4d65477   
k = cb0abc7043a10783684556fb12c4154d57bc31a289685f25  
R = 6994d962bdd0d793ffddf855ec5bf2f91a9698b46258a63e   
S = 02ba6465a234903744ab02bc8521405b73cf5fc00e1a9f41

I am trying to calculate $k_{inv}$ from given $k$ value and I am using curve “NID_X9_62_prime192v1”.

Can anyone tell me how to calculate $k_{inv}$?

share|improve this question
1  
Closely related to this question –  fgrieu Sep 16 at 6:41

1 Answer 1

Just compute the multiplicative inverse $k^{-1}$ of $k$ modulo the prime order $n$ of the base point $G$ (I used the typical notation for the domain parameters of the curve). This can efficiently be done using extended Euclid and should be available in any reasonable big integer library (typically something like modinverse). Thats it.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.