HMAC SHA256 in Swift 4

Question

I have a string and a key, which i want to generate an HMAC SHA256 from it. Although i\'m using 2 libs

IDZSwiftCommonCrypto and CryptoSwift

and this answer

Answer 1

Swift 4.2 solution for HMAC encryption

Not so long ago I had the same problem, so I wrote simple framework for use in Swift on all platforms - iOS macOS and tvOS

It's called EasyCrypt and you can find it here: https://github.com/lukszar/EasyCrypt

This framework let you encrypt message with your key, using HMAC algorithms. Usage is simple, like following:

let crypto = EasyCrypt(secret: "mySecretKey", algorithm: .sha256)
let result = crypto.hash("This is very secret text to encrypt")
let otherResult = crypto.hash("This is another secret text to encrypt")

print("result: ", result)
print("otherResult: ", otherResult)

You can fast install using Carthage. Inside project you can find Playground for demo usage with instructions.

Answer 2

I've been using this:

import Foundation

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

    var HMACAlgorithm: 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)
    }

    var digestLength: Int {
        var result: Int32 = 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: CryptoAlgorithm, key: String) -> String {
        let str = self.cString(using: String.Encoding.utf8)
        let strLen = Int(self.lengthOfBytes(using: String.Encoding.utf8))
        let digestLen = algorithm.digestLength
        let result = UnsafeMutablePointer<CUnsignedChar>.allocate(capacity: digestLen)
        let keyStr = key.cString(using: String.Encoding.utf8)
        let keyLen = Int(key.lengthOfBytes(using: String.Encoding.utf8))

        CCHmac(algorithm.HMACAlgorithm, keyStr!, keyLen, str!, strLen, result)

        let digest = stringFromResult(result: result, length: digestLen)

        result.deallocate(capacity: digestLen)

        return digest
    }

    private func stringFromResult(result: UnsafeMutablePointer<CUnsignedChar>, length: Int) -> String {
        let hash = NSMutableString()
        for i in 0..<length {
            hash.appendFormat("%02x", result[i])
        }
        return String(hash).lowercased()
    }
}

You'll need to add #import <CommonCrypto/CommonHMAC.h> to your Objective-C bridging header.

Source: @thevalyreangroup on this github thread

Answer 3

You're doing it wrong with CryptoSwift.

For future readers, here's how to do it:

let result = try! HMAC(key: key, variant: .sha256).authenticate(message.bytes)