Generate an RSA public / private key pair

Question

I'm looking for the simplest way to generate an RSA public / private key pair in swift I've been seeing a lot talk about how iOS doesn't support OpenSSL.

I simply need to generate the key pair and send the public key over to my server, the server will encrypt some data with the key and send it back over for my private key to decrypt. This is a one time transaction and I wont need the key anymore after that.

What is the simplest and lightest solution for this?

Answer 1

This Github repo - Heimdall, should help you with generating keys and encrypting your data.

Example usage:

if let heimdall = Heimdall(tagPrefix: "com.example") {
    let testString = "This is a test string"
// Encryption/Decryption
if let encryptedString = heimdall.encrypt(testString) {
    println(encryptedString) // "cQzaQCQLhAWqkDyPoHnPrpsVh..."

    if let decryptedString = heimdall.decrypt(encryptedString) {
        println(decryptedString) // "This is a test string"
    }
}

// Signatures/Verification
if let signature = heimdall.sign(testString) {
    println(signature) // "fMVOFj6SQ7h+cZTEXZxkpgaDsMrki..."
    var verified = heimdall.verify(testString, signatureBase64: signature)
    println(verified) // True

    // If someone meddles with the message and the signature becomes invalid
    verified = heimdall.verify(testString + "injected false message",
                                signatureBase64: signature)
    println(verified) // False
}

Encrypting data with own public key:

The swift-rsautils by btnguyen2k Utils should help you with encrypting your data with your own public key. Its really simple to use.

How to use:

First just drag and drop the RSAUtils.swift file to your project.

And thats it!

Encrypting basic string:

let PUBLIC_KEY = "MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAJh+/sdLdlVVcM5V5/j/RbwM8SL++Sc3dMqMK1nP73XYKhvO63bxPkWwaY0kwcUU40+QducwjueVOzcPFvHf+fECAwEAAQ=="

let sampleText:String = "WHATS UP"

let encrypted:NSData? = RSAUtils.encryptWithRSAPublicKey(sampleText.dataUsingEncoding(NSUTF8StringEncoding)!, pubkeyBase64: PUBLIC_KEY, keychainTag: "yourdomain.com")

let encryptedDataText = encrypted!.base64EncodedStringWithOptions(NSDataBase64EncodingOptions())

print(encryptedDataText)

This prints:

ML5S87dfDB6l1uHFcACm2IdkGHpDGPUaYoSNTO+83qcWYxTEddFeKhETIcqF5n67nRDL0lKi5XV9uEI7hGTyKA==