(Go) CMS Sign Hash

Demonstrates how to use the SignHashENC method to sign a pre-computed hash. This method creates a CMS signature (PKCS7 detached signature).

This example requires Chilkat v9.5.0.90 or later.

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

    crypt := chilkat.NewCrypt2()

    // Create the hash to be signed...
    crypt.SetHashAlgorithm("sha256")
    crypt.SetEncodingMode("base64")
    crypt.SetCharset("utf-8")
    // Create the SHA256 hash of a string using the utf-8 byte representation.
    // Return the hash as base64.
    base64Hash := crypt.HashStringENC("This is the string to be hashed")

    // Load a certificate for signing.
    cert := chilkat.NewCert()
    success := cert.LoadPfxFile("qa_data/pfx/cert_test123.pfx","test123")
    if success == false {
        fmt.Println(cert.LastErrorText())
        crypt.DisposeCrypt2()
        cert.DisposeCert()
        return
    }

    crypt.SetSigningCert(cert)

    // Sign the hash to create a base64 CMS signature (which does not contain the original data).
    // We can get the signature in a single line of base64 by specifying "base64", or 
    // we can get multi-line base64 by specifying "base64_mime".
    crypt.SetEncodingMode("base64_mime")
    base64CmsSig := crypt.SignHashENC(*base64Hash,"sha256","base64")
    if crypt.LastMethodSuccess() == false {
        fmt.Println(crypt.LastErrorText())
        crypt.DisposeCrypt2()
        cert.DisposeCert()
        return
    }

    // Note: In the above call to SignHashENC, the encoding of the returned CMS signature is specified by the EncodingMode property.
    // However, the encoding of the passed-in hash is indicated by the 3rd argument.

    fmt.Println("CMS Signature: ", *base64CmsSig)

    crypt.DisposeCrypt2()
    cert.DisposeCert()