(DataFlex) RSASSA-PSS Sign String to Create Base64 PCKS7 Signature

Signs a string to create a PKCS7 signature in the base64 encoding. The signature algorithm is RSASSA-PSS with SHA256.

Note: This example requires Chilkat v9.5.0.67 or greater.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

Use ChilkatAx-win32.pkg

Procedure Test
    Handle hoCrypt
    Handle hoPfx
    Boolean iSuccess
    Variant vCert
    Handle hoCert
    String sOriginalText
    String sPkcs7sig
    String sOpaqueSig
    String sOrigTxt
    String sTemp1
    Boolean bTemp1

    // This example requires the Chilkat Crypt API to have been previously unlocked.
    // See Unlock Chilkat Crypt for sample code.

    Get Create (RefClass(cComChilkatCrypt2)) To hoCrypt
    If (Not(IsComObjectCreated(hoCrypt))) Begin
        Send CreateComObject of hoCrypt
    End

    // Get a digital certificate with private key from a .pfx
    // (Chilkat has many different ways to provide a cert + private key for siging.
    // Using a PFX is just one possible option.)
    Get Create (RefClass(cComChilkatPfx)) To hoPfx
    If (Not(IsComObjectCreated(hoPfx))) Begin
        Send CreateComObject of hoPfx
    End
    Get ComLoadPfxFile Of hoPfx "qa_data/rsassa-pss/privatekey.pfx" "PFX_PASSWORD" To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoPfx To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Get the certificate to be used for signing.
    // (The typical case for a PFX is that it contains a cert with an associated private key,
    // as well as other certificates in the chain of authentication.  The cert with the private
    // key should be in the first position at index 0.)
    Get ComGetCert Of hoPfx 0 To vCert
    If (IsComObject(vCert)) Begin
        Get Create (RefClass(cComChilkatCert)) To hoCert
        Set pvComObject Of hoCert To vCert
    End
    Get ComLastMethodSuccess Of hoPfx To bTemp1
    If (bTemp1 <> True) Begin
        Get ComLastErrorText Of hoPfx To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get ComSetSigningCert Of hoCrypt vCert To iSuccess

    // Indicate that RSASSA-PSS with SHA256 should be used.
    Set ComSigningAlg Of hoCrypt To "pss"
    Set ComHashAlgorithm Of hoCrypt To "sha256"

    Set ComEncodingMode Of hoCrypt To "base64"

    // Sign a string and return the base64 PKCS7 detached signature
    Move "This is a test" To sOriginalText
    Get ComSignStringENC Of hoCrypt sOriginalText To sPkcs7sig
    Showln "Detached Signature:"
    Showln sPkcs7sig

    // This signature looks like this:
    // MIIG5wYJKoZIhvcNAQcCoIIG2DCCBtQCAQExDzANBgl .. YToLqEwTdU87ox5g7rvw==

    // The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
    // then copy-and-paste the Base64 signature into the form and decode..

    // The signature can be verified against the original data like this:
    Get ComVerifyStringENC Of hoCrypt sOriginalText sPkcs7sig To iSuccess
    Showln "Signature verified: " iSuccess
    Get ComVerifyStringENC Of hoCrypt "Not the original text" sPkcs7sig To iSuccess
    Showln "Signature verified: " iSuccess

    // Now we'll create an opaque signature (the opposite of a detached signature). 
    // An opaque signature is a PKCS7 message that contains both the original data and
    // the signature.  The verification process extracts the original data.
    Get ComOpaqueSignStringENC Of hoCrypt sOriginalText To sOpaqueSig
    Showln "Opaque Signature:"
    Showln sOpaqueSig

    // The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
    // then copy-and-paste the Base64 signature into the form and decode..

    // We can verify and extract the original data:
    Get ComOpaqueVerifyStringENC Of hoCrypt sOpaqueSig To sOrigTxt
    Get ComLastMethodSuccess Of hoCrypt To bTemp1
    If (bTemp1 <> True) Begin
        Showln "Signature verification failed."
        Get ComLastErrorText Of hoCrypt To sTemp1
        Showln sTemp1
        Send Destroy of hoCert
        Procedure_Return
    End

    Showln "Signature verified."
    Showln "Extracted text:" sOrigTxt

    Send Destroy of hoCert


End_Procedure