HMAC SHA256 in Swift 4
If you target iOS 13.0+ or macOS 10.15+, use Apple's CryptoKit
import CryptoKit
let secretString = "my-secret"
let key = SymmetricKey(data: Data(secretString.utf8))
let string = "An apple a day keeps anyone away, if you throw it hard enough"
let signature = HMAC<SHA256>.authenticationCode(for: Data(string.utf8), using: key)
print(Data(signature).map { String(format: "%02hhx", $0) }.joined()) // 1c161b971ab68e7acdb0b45cca7ae92d574613b77fca4bc7d5c4effab89dab67
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