(Go) Create and Verify an Opaque PKCS7/CMS Signature

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.

Chilkat Go Downloads Go Package for Windows, MacOS, Linux, Alpine Linux, Solaris

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

    crypt := chilkat.NewCrypt2()

    // 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

    cert := chilkat.NewCert()
    // The LoadFromFile method will automatically detect the format and load it.
    success := cert.LoadFromFile("qa_data/certs/test_12345678a.cer")
    if success != true {
        fmt.Println(cert.LastErrorText())
        crypt.DisposeCrypt2()
        cert.DisposeCert()
        return
    }

    // 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..
    privKey := chilkat.NewPrivateKey()
    password := "12345678a"
    success = privKey.LoadPkcs8EncryptedFile("qa_data/certs/test_12345678a.key",password)
    if success != true {
        fmt.Println(privKey.LastErrorText())
        crypt.DisposeCrypt2()
        cert.DisposeCert()
        privKey.DisposePrivateKey()
        return
    }

    // Set properties required for signing.

    // Tell it to use the cert and private key we've loaded.
    success = crypt.SetSigningCert2(cert,privKey)
    if success != true {
        fmt.Println(crypt.LastErrorText())
        crypt.DisposeCrypt2()
        cert.DisposeCert()
        privKey.DisposePrivateKey()
        return
    }

    // Indicate we want the opaque signature in base64 format:
    crypt.SetEncodingMode("base64")

    // Sign the string using the "utf-8" byte representation:
    crypt.SetCharset("utf-8")

    // Create the opaque signature:
    originalData := "This is the string to be signed."
    opaqueSig := crypt.OpaqueSignStringENC(originalData)
    if crypt.LastMethodSuccess() != true {
        fmt.Println(crypt.LastErrorText())
        crypt.DisposeCrypt2()
        cert.DisposeCert()
        privKey.DisposePrivateKey()
        return
    }

    fmt.Println(*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...

    vCrypt := chilkat.NewCrypt2()

    vCrypt.SetEncodingMode("base64")
    vCrypt.SetCharset("utf-8")

    extractedData := vCrypt.OpaqueVerifyStringENC(*opaqueSig)
    if vCrypt.LastMethodSuccess() != true {
        fmt.Println(vCrypt.LastErrorText())
        crypt.DisposeCrypt2()
        cert.DisposeCert()
        privKey.DisposePrivateKey()
        vCrypt.DisposeCrypt2()
        return
    }

    fmt.Println("The extracted data: ", *extractedData)

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

    crypt.DisposeCrypt2()
    cert.DisposeCert()
    privKey.DisposePrivateKey()
    vCrypt.DisposeCrypt2()