Sign with ECDH using Cryptography API: Next Generation C++

Question

The Signing Data with CNG example, shows how to sign and verify using ECDSA.

I changed the code:
BCRYPT_ECDSA_P256_ALGORITHM to BCRYPT_ECDH_P256_ALGORITHM
NCRYPT_ECDSA_P256_ALGORITHM to NCRYPT_ECDH_P256_ALGORITHM

However, the signature verification fails. I can not imagine why it does not work.

I am using Windows 7 64 bits; Visual Studio 2010; Debug; win32 mode.

Articles are very welcome.

Why would you switch from a digital signature algorithm to a key agreement algorithm in the first place? — Maarten Bodewes, Mar 09 '12 at 23:29
@GregS Perfect, thanks. This is the point. Can you post it as answer!? — Cobaia, Mar 12 '12 at 12:09

score 1 · Accepted Answer · answered Mar 12 '12 at 22:18

1

ECDH is not a signature algorithm. Therefore, you cannot sign with it.

answered Mar 12 '12 at 22:18

What if you try *really really* hard to use it for signing anyway? – Jumbogram Mar 13 '12 at 00:47
@Jumbogram: if you try hard enough, and I mean *really really really* hard, then it transmutes to ECDSA and will work for signing. – President James K. Polk Mar 13 '12 at 00:49
@Jumbogram Well, sometimes when you run out of API, you do things like using raw RSA to create DH. Thanks for the new word in my dictionary though :) – Maarten Bodewes Mar 16 '12 at 02:35
@owlstead: You know what that word is from, right? http://calvinandhobbes.wikia.com/wiki/Transmogrifier – Jumbogram Mar 17 '12 at 15:53

1 Answers1