Sample code for 30+ languages & platforms
DataFlex

Sign PDF: Choosing RSASSA-PSS or PKCS1-v1_5 and Hash Algorithm

See more PDF Signatures Examples

This example demonstrates how to choose between RSASSA-PSS vs. PKCS1-v1_5 and the hash algorithm when signing a PDF.

Chilkat DataFlex Downloads

Download Chilkat for DataFlex
DataFlex 
Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoPdf
    Variant vJson
    Handle hoJson
    Variant vCert
    Handle hoCert
    String sTemp1

    Move False To iSuccess

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

    Get Create (RefClass(cComChilkatPdf)) To hoPdf
    If (Not(IsComObjectCreated(hoPdf))) Begin
        Send CreateComObject of hoPdf
    End

    //  Load a PDF to be signed.
    //  The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
    Get ComLoadFile Of hoPdf "qa_data/pdf/hello.pdf" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoPdf To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    //  Options for signing are specified in JSON.
    Get Create (RefClass(cComChilkatJsonObject)) To hoJson
    If (Not(IsComObjectCreated(hoJson))) Begin
        Send CreateComObject of hoJson
    End

    //  In most cases, the signingCertificateV2 attribute is needed.
    Get ComUpdateInt Of hoJson "signingCertificateV2" 1 To iSuccess

    //  ---------------------------------------------------------------------------------------------------------------------------
    //  This example is the same as the example at Sign a PDF (Simplest Example Possible)
    //  but with the following lines added to specify the signature scheme and hash algorithm.

    //  The signature schemes PKCS-v1_5 and RSASSA-PSS have differences. 
    //  PKCSV1_5 is deterministic. The same message and key will produce an identical signature value each time. 
    //  PSS is randomized and will produce a different signature value each time.

    //  To choose the hash algorithm:
    //  (The typical choices are sha1, sha256, sha384, and sha512.)
    Get ComUpdateString Of hoJson "hashAlgorithm" "sha256" To iSuccess

    //  To choose PKCSV1_5:
    Get ComUpdateString Of hoJson "signingAlgorithm" "pkcs" To iSuccess
    //  Alternatively, to choose RSASSA-PSS:
    Get ComUpdateString Of hoJson "signingAlgorithm" "pss" To iSuccess

    //  If not specified, the default is SHA256 with PKCS-v1_5.

    //  The remainder of this example is the same as the example at Sign a PDF (Simplest Example Possible)
    //  ---------------------------------------------------------------------------------------------------------------------------

    //  Put the signature on page 1, top left
    Get ComUpdateInt Of hoJson "page" 1 To iSuccess
    Get ComUpdateString Of hoJson "appearance.y" "top" To iSuccess
    Get ComUpdateString Of hoJson "appearance.x" "left" To iSuccess

    //  Use a font scale of 10.0
    Get ComUpdateString Of hoJson "appearance.fontScale" "10.0" To iSuccess

    //  In this example, the appearance of the digital signature will contain three lines:
    //  1) The signing certificate's common name
    //  2) The current date/time
    //  3) Some arbitrary text.
    //  The keyword "cert_cn" is replaced with the Certificate's Subject Common Name.
    //  The keyword "current_dt" is replaced with the current date/time.
    //  Any number of appearance text lines can be added.
    Get ComUpdateString Of hoJson "appearance.text[0]" "Digitally signed by: cert_cn" To iSuccess
    Get ComUpdateString Of hoJson "appearance.text[1]" "current_dt" To iSuccess
    Get ComUpdateString Of hoJson "appearance.text[2]" "The crazy brown fox jumps over the lazy dog." To iSuccess

    //  Load the signing certificate. (Use your own certificate.)
    Get Create (RefClass(cComChilkatCert)) To hoCert
    If (Not(IsComObjectCreated(hoCert))) Begin
        Send CreateComObject of hoCert
    End
    Get ComLoadPfxFile Of hoCert "qa_data/pfx/myPdfSigningCert.pfx" "secret" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoCert To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    //  Tell the pdf object to use the certificate for signing.
    Get pvComObject of hoCert to vCert
    Get ComSetSigningCert Of hoPdf vCert To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoPdf To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get pvComObject of hoJson to vJson
    Get ComSignPdf Of hoPdf vJson "qa_output/hello_signed.pdf" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoPdf To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Showln "The PDF has been successfully cryptographically signed."

    //  The appearance of the signature appears in Adobe Acrobat as shown here:

    //  image


End_Procedure