(CkPython) Create JWS Using Private Key on a Smart Card

See more JSON Web Signatures (JWS) Examples

Creates and validates a JSON Web Signature (JWS) using the private key associated with a certificate on a smart card.

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

# Load the certificate from a smart card.
cert = chilkat.CkCert()
success = cert.LoadFromSmartcard("")
if (success == False):
    print(cert.lastErrorText())
    sys.exit()

# Note: Chilkat provides many different ways to load a certificate from a smartcard or USB token,
# such as selecting a certificate if the card contains multiple certificates with private keys,
# or working with lower-level PKCS11 or ScMinidriver API's (both of which Chilkat provides).

# If the associated private key was present on the smartcard, then you can simply
# get it from the Chilkat cert object:
# privKey is a CkPrivateKey
privKey = cert.ExportPrivateKey()
if (cert.get_LastMethodSuccess() == False):
    print(cert.lastErrorText())
    sys.exit()

# You can check the key type to make sure it's RSA.
# This will output "rsa" if the key is RSA.
print("Key type = " + privKey.keyType())

# Create the JWS Protected Header
jwsProtHdr = chilkat.CkJsonObject()
jwsProtHdr.AppendString("alg","RS256")

jws = chilkat.CkJws()

# Set the protected header:
signatureIndex = 0
jws.SetProtectedHeader(signatureIndex,jwsProtHdr)

# Set the RSA key:
jws.SetPrivateKey(signatureIndex,privKey)

# Set the payload.
bIncludeBom = False
payloadStr = "In our village, folks say God crumbles up the old moon into stars."
jws.SetPayload(payloadStr,"utf-8",bIncludeBom)

# Create the JWS
# By default, the compact serialization is used.
jwsCompact = jws.createJws()
if (jws.get_LastMethodSuccess() != True):
    print(jws.lastErrorText())

    sys.exit()

print("JWS: " + jwsCompact)

# sample output:
# JWS: eyJhbGciOiJQUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.TRWhwRo5dMv9-8OzrInfJTwmUGYgjLfHk8lqF072ND-FmLWEBnUTOpY8oJXp8FdWw2SalbdOeNlrtlJjwk4XK8Ql2iJ_2qMCtxsvLPhKBOqFoAF4aBvTOEDVJDxf0DaBSiydEEtfTVV2iwBcjWabu5J2XieR5y7QZQtuHsn7T3qKBvCcCejN3Y2oqAT3qMHvu1fTms1r_91wBn_K7Wjd9UkZ1n02qQcUHJznR_OF2BgN7_KWIDAF9ZS9keoju2NPpPelO4yxa2XUPnehY3G7dHKoCxUEQR4d2Xc5voqDASTVCDqQS4PVOZdvT3Ein6-SanAlCwbWBbkvT8g6-5PImQ

# Now load the JWS, validate, and recover the original text.
jws2 = chilkat.CkJws()

# Load the JWS.
success = jws2.LoadJws(jwsCompact)

# rsaPubKey is a CkPublicKey
rsaPubKey = privKey.GetPublicKey()

# Set the RSA public key used for validation.
signatureIndex = 0
jws2.SetPublicKey(signatureIndex,rsaPubKey)

# Validate the 1st (and only) signature at index 0..
v = jws2.Validate(signatureIndex)
if (v < 0):
    # Perhaps Chilkat was not unlocked or the trial expired..
    print("Method call failed for some other reason.")
    print(jws2.lastErrorText())
    sys.exit()

if (v == 0):
    print("Invalid signature.  The RSA key was incorrect, the JWS was invalid, or both.")
    sys.exit()

# If we get here, the signature was validated..
print("Signature validated.")

# Recover the original content:
print(jws2.getPayload("utf-8"))

# Examine the protected header:
# joseHeader is a CkJsonObject
joseHeader = jws2.GetProtectedHeader(signatureIndex)
if (jws2.get_LastMethodSuccess() != True):
    print("No protected header found at the given index.")
    sys.exit()

joseHeader.put_EmitCompact(False)

print("Protected (JOSE) header:")
print(joseHeader.emit())

# Output:

# 	Signature validated.
# 	In our village, folks say God crumbles up the old moon into stars.
# 	Protected (JOSE) header:
# 	{ 
# 	  "alg": "RS256"
# 	}