PKCS7 SignedData Detached Signature

How to create a PKCS7 detached signature. The resulting PKCS7 structure is encoded to a printable string using hex or base64 encoding. The data being signed is not included in the PKCS#7 structure.

Download Chilkat Python Library

import sys
import chilkat

crypt = chilkat.CkCrypt2()

#  Any string argument automatically begins the 30-day trial.
success = crypt.UnlockComponent("30-day trial")
if (success != True):
    print "Crypt component unlock failed"
    sys.exit()

cert = chilkat.CkCert()
success = cert.LoadByCommonName("Chilkat Software")
if (success != True):
    print cert.lastErrorText()
    sys.exit()

#  Make sure this certificate has a private key available:

bHasPrivateKey = cert.HasPrivateKey()
if (bHasPrivateKey != True):
    print "No private key available for signing."
    sys.exit()

#  Tell the encryption component to use this cert.
crypt.SetSigningCert(cert)

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

#  Indicate that the PKCS7 signature should be returned
#  as a base64 encoded string:
crypt.put_EncodingMode("base64")

#  The EncodingMode may be set to other values such as
#  "hex", "url", "quoted-printable", etc.

strSignature = crypt.signStringENC(strData)

print strSignature

#  Now verify the signature against the original data.

#  Tell the component what certificate to use for verification.
crypt.SetVerifyCert(cert)

success = crypt.VerifyStringENC(strData,strSignature)
if (success == True):
    print "digital signature verified"
else:
    print "digital signature invalid"

#  Try it with incorrect data:
success = crypt.VerifyStringENC("This is not the signed data",strSignature)
if (success == True):
    print "digital signature verified"
else:
    print "digital signature invalid"