How do I feed OpenSSL random data for use in ECDSA signing?

Question

I want to feed OpenSSL specific data for use as random seed during the signing of data with an EC key. I\'m doing this to compare my application with another reference one (

Answer 1

The signing procedure is purely to allow someone else to confirm that you signed it ie. it was your private key that was used to sign the message (or any data) without actually having your private key.

The algorithm is outlined on wikipedia Elliptic_Curve_DSA Reading "Signature generation algorithm" it appears the random data is used to assist in the strength of the signature and to make it harder to attack to figure out the private key.

Therefore you should expect the signature to be different each time since this is not just simply a hash.

See the section "Signature verification algorithm" to see that the verification steps are the ones you wish to use to confirm that your openssl version is outputing valid signatures w.r.t. the ECDSA method and the closed source program.