(Swift 3,4,5...) Duplicate openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

Demonstrates how to duplicate this OpenSSL command:

openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

1. Creates a SHA256 digest of the contents of the input file.
2. Verifies the SHA256 digest using the public key.

Chilkat Downloads for the Swift Programming Language MAC OS X (Cocoa) Objective-C/Swift Libs iOS Objective-C/Swift Libs

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

    let pubKey = CkoPublicKey()!

    // Load the public key from an PEM file:
    var success: Bool = pubKey.load(fromFile: "pubKey.pem")
    if success != true {
        print("\(pubKey.lastErrorText!)")
        return
    }

    // Load the data of the original file that was signed.
    let bdFileData = CkoBinData()!
    success = bdFileData.loadFile("in.dat")

    // Load the signature.
    let bdSig = CkoBinData()!
    success = bdSig.loadFile("signature.sig")

    let rsa = CkoRsa()!

    // Import the public key into the RSA component:
    success = rsa.importPublicKeyObj(pubKey)
    if success != true {
        print("\(rsa.lastErrorText!)")
        return
    }

    // OpenSSL uses big-endian.
    rsa.littleEndian = false

    success = rsa.verifyBd(bdFileData, hashAlgorithm: "sha256", bdSig: bdSig)
    if success != true {
        print("\(rsa.lastErrorText!)")
        print("The signature was invalid.")
        return
    }

    print("The signature was verified.")

}