(Chilkat2-Python) Verify the RSA Signature of a SHA256 Hash

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Demonstrates how to verify an RSA signature of a SHA256 hash.

Chilkat2 Python Downloads install with pip pip3 install chilkat2 or download... Python Module for Windows, Linux, Alpine Linux, MacOS, Solaris

import sys
import chilkat2

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

# Let's say you have a file containing the 32-bytes of a SHA256 hash,
# and a file that is an RSA signature of those 32 bytes.
# Here's how you verify using the RSA public key found in a PEM.

pubKey = chilkat2.PublicKey()
success = pubKey.LoadFromFile("rsaPubKey.pem")
if (success == False):
    print(pubKey.LastErrorText)
    sys.exit()

rsa = chilkat2.Rsa()

# Get the public key.
success = rsa.ImportPublicKeyObj(pubKey)
if (success == False):
    print(rsa.LastErrorText)
    sys.exit()

# Get the 32-byte SHA256 hash.
bdHash = chilkat2.BinData()
success = bdHash.LoadFile("myHash.sha256")
if (success == False):
    print("Failed to load SHA256 hash.")
    sys.exit()

# Get the RSA signature to be validated.
bdSig = chilkat2.BinData()
success = bdSig.LoadFile("mySig.sig")
if (success == False):
    print("Failed to load RSA signature.")
    sys.exit()

# Verify the signature against the SHA256 hash.
enc = "base64"
rsa.EncodingMode = enc
success = rsa.VerifyHashENC(bdHash.GetEncoded(enc),"sha256",bdSig.GetEncoded(enc))
if (success == False):
    print(rsa.LastErrorText)
    sys.exit()

print("Signature validated.")