(Swift 2) ECDSA Sign and Verify Data using Different Hash Algorithms

Demonstrates how to create ECDSA signatures on data using different hash algorithms.

Note: This example requires Chilkat v9.5.0.85 or greater because the SignBd and VerifyBd methods were added in v9.5.0.85.

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

    // First load an ECDSA private key to be used for signing.
    let privKey = CkoPrivateKey()
    var success: Bool = privKey.LoadEncryptedPemFile("qa_data/ecc/secp256r1-key-pkcs8-secret.pem", password: "secret")
    if success == false {
        print("\(privKey.LastErrorText)")
        return
    }

    // Load some data to be signed.
    let bd = CkoBinData()
    success = bd.LoadFile("qa_data/hamlet.xml")
    if success == false {
        print("Failed to load file to be hashed.")
        return
    }

    let ecdsa = CkoEcc()
    let prng = CkoPrng()

    // Sign the sha256 hash of the data.  Return the ECDSA signature in the base64 encoding.
    print("ECDSA signing the sha256 hash of the data...")
    var sig: String? = ecdsa.SignBd(bd, hashAlg: "sha256", encoding: "base64", privKey: privKey, prng: prng)
    print("sig = \(sig!)")

    // Verify the signature against the original data.
    // (We must use the same hash algorithm that was used when signing.)

    // Load the public key that corresponds to the private key used for signing.
    let pubKey = CkoPublicKey()
    success = pubKey.LoadFromFile("qa_data/ecc/secp256r1-pub.pem")
    if success == false {
        print("\(pubKey.LastErrorText)")
        return
    }

    let ecc2 = CkoEcc()
    var result: Int = ecc2.VerifyBd(bd, hashAlg: "sha256", encodedSig: sig, encoding: "base64", pubkey: pubKey).intValue
    if result != 1 {
        print("\(ecc2.LastErrorText)")
        return
    }

    print("Verified!")

    // ----------------------------------------------------------------------------------------
    // Let's do the same thing, but with sha384 hashing...

    print("--------------------------------------------")
    print("ECDSA signing the sha384 hash of the data...")

    sig = ecdsa.SignBd(bd, hashAlg: "sha384", encoding: "base64", privKey: privKey, prng: prng)
    print("sig = \(sig!)")

    result = ecc2.VerifyBd(bd, hashAlg: "sha384", encodedSig: sig, encoding: "base64", pubkey: pubKey).intValue
    if result != 1 {
        print("\(ecc2.LastErrorText)")
        return
    }

    print("Verified!")

}