Swift

Verify an RSA Signature Against the Signed String

See more Apple Keychain Examples

Demonstrates how to validate an RSA Signature against the string that was signed. Swift

func chilkatTest() {
    var success: Bool = false

    // Create the same string we previously signed in this example: 
    // RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

    let sb = CkoStringBuilder()!
    var crlfLineEnding: Bool = true
    var i: Int
    for i = 0; i <= 10; i++ {
        sb.appendLine(str: "This is a test.", crlf: crlfLineEnding)
    }

    var base64_rsa_sig: String? = "gWgpEXQqvXN6wh0MuFXPiw2xCb8cnmdizBT1TD1Tpm2GlJ8gnD59DGSj35GGXk1tM+mCOvMa2uW/9gmz8p6A90JLbn918i/2wKGvcde4wXnzPO7JADSNn2UwYzf3rp4/q/JrHv1GZETRJhABSFqTxOgdmdbEJQE/zijOSctCtQAM2CTb6t2BO8uHKSSUAwPH2cbeWxqsaVRLT4ruk5nZOxhoLgLMSjupiSzbE8zSTkkFOEHD+Mbb2xwg85AI0E4DsUnp+hLwwtS0blesgSyvtBY8oJODJeFcJsR7JDOTPdzHQHgJRl/2A4ij5xT91TpXy7ok43jhT6O9j7Q3qrafIQ=="

    // Get the public key to be used for signature verification.
    let pubKey = CkoPublicKey()!
    success = pubKey.load(fromFile: "rsaKeys/chilkat-rsa-2048.pem")
    if success == false {
        print("\(pubKey.lastErrorText!)")
        return
    }

    let rsa = CkoRsa()!
    success = rsa.usePublicKey(pubKey: pubKey)
    if success == false {
        print("\(rsa.lastErrorText!)")
        return
    }

    // Verify the string against the signature.
    // We signed the utf-8 byte representation of the string, so we must indicate
    // to also validate against the utf-8 byte representation.
    rsa.charset = "utf-8"
    rsa.encodingMode = "base64"
    var signedString: String? = sb.getAsString()
    success = rsa.verifyStringENC(str: signedString, hashAlg: "sha256", sig: base64_rsa_sig)

    if success == false {
        print("\(rsa.lastErrorText!)")
        print("Signature invalid.")
    }
    else {
        print("Signature valid.")
    }


}