(Chilkat2-Python) Verify an RSA Signature Against the Signed String

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Demonstrates how to validate an RSA Signature against the string that was signed.

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

import sys
import chilkat2

# Create the same string we previously signed in this example: 
# RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

sb = chilkat2.StringBuilder()
crlfLineEnding = True

for i in range(0,11):
    sb.AppendLine("This is a test.",crlfLineEnding)

base64_rsa_sig = "gWgpEXQqvXN6wh0MuFXPiw2xCb8cnmdizBT1TD1Tpm2GlJ8gnD59DGSj35GGXk1tM+mCOvMa2uW/9gmz8p6A90JLbn918i/2wKGvcde4wXnzPO7JADSNn2UwYzf3rp4/q/JrHv1GZETRJhABSFqTxOgdmdbEJQE/zijOSctCtQAM2CTb6t2BO8uHKSSUAwPH2cbeWxqsaVRLT4ruk5nZOxhoLgLMSjupiSzbE8zSTkkFOEHD+Mbb2xwg85AI0E4DsUnp+hLwwtS0blesgSyvtBY8oJODJeFcJsR7JDOTPdzHQHgJRl/2A4ij5xT91TpXy7ok43jhT6O9j7Q3qrafIQ=="

# Get the public key to be used for signature verification.
pubKey = chilkat2.PublicKey()
success = pubKey.LoadFromFile("rsaKeys/chilkat-rsa-2048.pem")
if (success == False):
    print(pubKey.LastErrorText)
    sys.exit()

rsa = chilkat2.Rsa()
rsa.ImportPublicKeyObj(pubKey)

# Verify the string against the signature.
# We signed the utf-8 byte representation of the string, so we must indicate
# to also validate against the utf-8 byte representation.
rsa.Charset = "utf-8"
rsa.EncodingMode = "base64"
signedString = sb.GetAsString()
success = rsa.VerifyStringENC(signedString,"sha256",base64_rsa_sig)

if (success == False):
    print(rsa.LastErrorText)
    print("Signature invalid.")
else:
    print("Signature valid.")