Chilkat2-Python

RSA Signature/Verify with .key and .cer

See more RSA Examples

Demonstrates how to use a .key file (private key) and digital certificate (.cer, public key) to create and verify an RSA signature. Chilkat2-Python

import sys
import chilkat2

success = False

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

privKey = chilkat2.PrivateKey()

# Load the private key from an RSA .key file:
success = privKey.LoadPemFile("privateKey.key")
if (success == False):
    print(privKey.LastErrorText)
    sys.exit()

rsa = chilkat2.Rsa()

# Import the private key into the RSA component:
success = rsa.UsePrivateKey(privKey)
if (success == False):
    print(rsa.LastErrorText)
    sys.exit()

# Create the signature as a hex string:
rsa.EncodingMode = "hex"

strData = "This is the string to be signed."

# Sign the string using the sha256 hash algorithm.
# Other valid choices are "md2", "sha1", "sha384",
# "sha512", and "md5".
hexSig = rsa.SignStringENC(strData,"sha256")

print(hexSig)

# Load a digital certificate from a .cer file:
cert = chilkat2.Cert()

success = cert.LoadFromFile("myCert.cer")
if (success == False):
    print(cert.LastErrorText)
    sys.exit()

pubKey = chilkat2.PublicKey()
cert.GetPublicKey(pubKey)

# Now verify using a new instance of the RSA object:
rsa2 = chilkat2.Rsa()

# Import the public key into the RSA object:
success = rsa2.UsePublicKey(pubKey)
if (success == False):
    print(rsa2.LastErrorText)
    sys.exit()

# The signature is a hex string, so make sure the EncodingMode is correct:
rsa2.EncodingMode = "hex"

# Verify the signature:
success = rsa2.VerifyStringENC(strData,"sha256",hexSig)
if (success == False):
    print(rsa2.LastErrorText)
    sys.exit()

print("Success.")