Tcl

Create and Verify an Opaque PKCS7/CMS Signature

See more Digital Signatures Examples

Demonstrates how to create a PKCS7 opaque signature, and also how to verify an opaque signature. An opaque signature is different than a detached PKCS7 signature in that it contains the original data. Verifying an opaque signature retrieves the original content. Tcl

load ./chilkat.dll

set success 0

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

set crypt [new_CkCrypt2]

# A certificate and private key is needed to create a signature.
# Chilkat provides many different ways to load a certificate and private key, such
# as from a PFX/.p12, Java keystore, JWK, Windows registry-based certificate stores, and other sources.
# This example will load the certificate from a .crt and the private key from a .key file

set cert [new_CkCert]

# The LoadFromFile method will automatically detect the format and load it.
set success [CkCert_LoadFromFile $cert "qa_data/certs/test_12345678a.cer"]
if {$success != 1} then {
    puts [CkCert_lastErrorText $cert]
    delete_CkCrypt2 $crypt
    delete_CkCert $cert
    exit
}

# Our private key is in an encrypted PKCS8 format.
# If you don't know the format of your key, but you do know it's encrypted,
# and requires a password, then just call any of the Chilkat methods that load
# a private key w/ a password argument.  Chilkat will auto-detect the format
# and load it correctly even if it's not the format indicated by the method name..
set privKey [new_CkPrivateKey]

set password "12345678a"
set success [CkPrivateKey_LoadPkcs8EncryptedFile $privKey "qa_data/certs/test_12345678a.key" $password]
if {$success != 1} then {
    puts [CkPrivateKey_lastErrorText $privKey]
    delete_CkCrypt2 $crypt
    delete_CkCert $cert
    delete_CkPrivateKey $privKey
    exit
}

# Set properties required for signing.

# Tell it to use the cert and private key we've loaded.
set success [CkCrypt2_SetSigningCert2 $crypt $cert $privKey]
if {$success != 1} then {
    puts [CkCrypt2_lastErrorText $crypt]
    delete_CkCrypt2 $crypt
    delete_CkCert $cert
    delete_CkPrivateKey $privKey
    exit
}

# Indicate we want the opaque signature in base64 format:
CkCrypt2_put_EncodingMode $crypt "base64"

# Sign the string using the "utf-8" byte representation:
CkCrypt2_put_Charset $crypt "utf-8"

# Create the opaque signature:
set originalData "This is the string to be signed."
set opaqueSig [CkCrypt2_opaqueSignStringENC $crypt $originalData]
if {[CkCrypt2_get_LastMethodSuccess $crypt] != 1} then {
    puts [CkCrypt2_lastErrorText $crypt]
    delete_CkCrypt2 $crypt
    delete_CkCert $cert
    delete_CkPrivateKey $privKey
    exit
}

puts "$opaqueSig"

# The output looks like this:
# MIIPgQYJKoZIhvcNAQcCoIIPcjCCD24CAQExCzAJBgUrDgMCGgUAMC8GCSqGSIb3DQEHAaAiBCBUaGlzIGlzIHRoZSBzdHJpbmcgdG8gYmUgc...

# ----------------------------------------------------------------------------------------------
# Now let's verify the signature and retrieve the original data.
# We'll use a new Crypt2 object to keep things completely separate...

set vCrypt [new_CkCrypt2]

CkCrypt2_put_EncodingMode $vCrypt "base64"
CkCrypt2_put_Charset $vCrypt "utf-8"

set extractedData [CkCrypt2_opaqueVerifyStringENC $vCrypt $opaqueSig]
if {[CkCrypt2_get_LastMethodSuccess $vCrypt] != 1} then {
    puts [CkCrypt2_lastErrorText $vCrypt]
    delete_CkCrypt2 $crypt
    delete_CkCert $cert
    delete_CkPrivateKey $privKey
    delete_CkCrypt2 $vCrypt
    exit
}

puts "The extracted data: $extractedData"

# The output is:
# The extracted data: This is the string to be signed.

delete_CkCrypt2 $crypt
delete_CkCert $cert
delete_CkPrivateKey $privKey
delete_CkCrypt2 $vCrypt