Implementing HMAC and SHA1 encryption in swift

Question

I am relatively new to Swift and i\'m stuck encrypting using HMAC and SHA1. I Found the following answer https://stackoverflow.com/a/24411522/4188344 but i can\'t work out h

Answer 1

Here is @David Wood's solution updated for Swift 3:

enum HMACAlgorithm {
    case MD5, SHA1, SHA224, SHA256, SHA384, SHA512

    func toCCHmacAlgorithm() -> CCHmacAlgorithm {
        var result: Int = 0
        switch self {
        case .MD5:
            result = kCCHmacAlgMD5
        case .SHA1:
            result = kCCHmacAlgSHA1
        case .SHA224:
            result = kCCHmacAlgSHA224
        case .SHA256:
            result = kCCHmacAlgSHA256
        case .SHA384:
            result = kCCHmacAlgSHA384
        case .SHA512:
            result = kCCHmacAlgSHA512
        }
        return CCHmacAlgorithm(result)
    }

    func digestLength() -> Int {
        var result: CInt = 0
        switch self {
        case .MD5:
            result = CC_MD5_DIGEST_LENGTH
        case .SHA1:
            result = CC_SHA1_DIGEST_LENGTH
        case .SHA224:
            result = CC_SHA224_DIGEST_LENGTH
        case .SHA256:
            result = CC_SHA256_DIGEST_LENGTH
        case .SHA384:
            result = CC_SHA384_DIGEST_LENGTH
        case .SHA512:
            result = CC_SHA512_DIGEST_LENGTH
        }
        return Int(result)
    }
}

extension String {
    func hmac(algorithm: HMACAlgorithm, key: String) -> String {
        let cKey = key.cString(using: String.Encoding.utf8)
        let cData = self.cString(using: String.Encoding.utf8)
        var result = [CUnsignedChar](repeating: 0, count: Int(algorithm.digestLength()))
        CCHmac(algorithm.toCCHmacAlgorithm(), cKey!, Int(strlen(cKey!)), cData!, Int(strlen(cData!)), &result)
        let hmacData:NSData = NSData(bytes: result, length: (Int(algorithm.digestLength())))
        let hmacBase64 = hmacData.base64EncodedString(options: NSData.Base64EncodingOptions.lineLength76Characters)
        return String(hmacBase64)
    }
}

// usage:
let hmacResult: String = "myStringToHMAC".hmac(algorithm: HMACAlgorithm.SHA1, key: "foo")

Answer 2

If you want the same result in hexadecimal format, you can use the following extension:

extension String {
    func hmac(algorithm: HMACAlgorithm, key: String) -> String {
        let cKey = key.cStringUsingEncoding(NSUTF8StringEncoding)
        let cData = self.cStringUsingEncoding(NSUTF8StringEncoding)
        var result = [CUnsignedChar](count: Int(algorithm.digestLength()), repeatedValue: 0)
        let length : Int = Int(strlen(cKey!))
        let data : Int = Int(strlen(cData!))
        CCHmac(algorithm.toCCHmacAlgorithm(), cKey!,length , cData!, data, &result)

        let hmacData:NSData = NSData(bytes: result, length: (Int(algorithm.digestLength())))

        var bytes = [UInt8](count: hmacData.length, repeatedValue: 0)
        hmacData.getBytes(&bytes, length: hmacData.length)

        var hexString = ""
        for byte in bytes {
            hexString += String(format:"%02hhx", UInt8(byte))
        }
        return hexString
    }
}