(CkPython) RSA Sign with PKCS8 Encrypted Key

Demonstrates how to load a private key from an encrypted PKCS8 file and create an RSA digital signature (and then verify it).

Note: This example requires Chilkat v11.0.0 or greater.

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import sys
import chilkat

success = False

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

privKey = chilkat.CkPrivateKey()

# Load the private key from an RSA PEM file:
success = privKey.LoadAnyFormatFile("raul_privateKey.key","a0123456789")
if (success == False):
    print(privKey.lastErrorText())
    sys.exit()

rsa = chilkat.CkRsa()

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

# This example will sign a string, and receive the signature
# in a hex-encoded string.  Therefore, set the encoding mode
# to "hex":
rsa.put_EncodingMode("hex")

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

# Sign the string using the sha256 hash algorithm.
# Other valid choices are sha1, sha384, sha512 and others.
hexSig = rsa.signStringENC(strData,"sha256")
if (rsa.get_LastMethodSuccess() == False):
    print(rsa.lastErrorText())
    sys.exit()

print(hexSig)

# Now verify with the public key.
# This example shows how to use the public key from 
# a digital certificate (.cer file)
cert = chilkat.CkCert()
success = cert.LoadFromFile("raul_publicKey.cer")
if (success == False):
    print(cert.lastErrorText())
    sys.exit()

pubKey = chilkat.CkPublicKey()
cert.GetPublicKey(pubKey)

rsa2 = chilkat.CkRsa()
success = rsa2.UsePublicKey(pubKey)
if (success == False):
    print(rsa2.lastErrorText())
    sys.exit()

# Verify the signature against the original data:
rsa2.put_EncodingMode("hex")
success = rsa2.VerifyStringENC(strData,"sha256",hexSig)
if (success == False):
    print(rsa2.lastErrorText())
    sys.exit()

print("Signature verified!")

# Verify with incorrect data:
success = rsa2.VerifyStringENC("something else","sha256",hexSig)
if (success != True):
    print("Signature not verified! (which was expected in this case)")
else:
    print("Hmmm... that's not right...")