(CkPython) Create ECSDA Signature using Raw r and s Format (not ASN.1)

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Demonstrates how to create an ECDSA signature using the raw r/s format.

ECDSA signatures have two equal sized parts, r and s. There are two common formats for encoding the signature:

(a) Concatenating the raw byte array of r and s
(b) Encoding both into a structured ASN.1 / DER sequence.

This example demonstrates how to create a signature that is a byte array of r and s concatenated.

Note: This example requires Chilkat v9.5.0.97 or greater.

Chilkat Python Downloads install with pip pip3 install chilkat or download... Python Module for Windows, MacOS, Linux, Alpine Linux, Solaris

import sys
import chilkat

# This example requires the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

# To create an ECDSA signature, the data first needs to be hashed.  Then the hash
# is signed.

sb = chilkat.CkStringBuilder()
sb.Append("The quick brown fox jumps over the lazy dog")
hash = sb.getHash("sha256","base64","utf-8")

# Load the ECDSA key to be used for signing.
privKey = chilkat.CkPrivateKey()
success = privKey.LoadPemFile("qa_data/ecc/secp256r1-key-pkcs8.pem")
if (success != True):
    print(privKey.lastErrorText())
    sys.exit()

prng = chilkat.CkPrng()
ecdsa = chilkat.CkEcc()

# Produce a signature that is not ASN.1, but is instead the concatenation
# of the raw r and s signature parts.
# This feature was added in Chilkat v9.5.0.97
ecdsa.put_AsnFormat(False)

ecdsaSigBase64 = ecdsa.signHashENC(hash,"base64",privKey,prng)
if (ecdsa.get_LastMethodSuccess() != True):
    print(ecdsa.lastErrorText())
    sys.exit()

print("ECDSA signature = " + ecdsaSigBase64)

# -----------------------------------------------------------
# Now let's verify the signature using the public key.

pubKey = chilkat.CkPublicKey()
success = pubKey.LoadFromFile("qa_data/ecc/secp256r1-pubkey.pem")
if (success != True):
    print(pubKey.lastErrorText())
    sys.exit()

# Note: When verifying, Chilkat will auto-detect the format for both kinds of ECDSA signatures (ASN.1 or binary r+s)
result = ecdsa.VerifyHashENC(hash,ecdsaSigBase64,"base64",pubKey)
if (result == 1):
    print("Signature is valid.")
    sys.exit()

if (result == 0):
    print("Signature is invalid.")
    sys.exit()

if (result < 0):
    print(ecdsa.lastErrorText())
    print("The VerifyHashENC method call failed.")
    sys.exit()