HMACSHA1Hash.swift

import CommonCrypto

extension String {
    func hmacSHA1Hash(key: String) -> String {
        var digest = [UInt8](repeating: 0, count: Int(CC_SHA1_DIGEST_LENGTH))
        CCHmac(CCHmacAlgorithm(kCCHmacAlgSHA1),
               key,
               key.count,
               self,
               self.count,
               &digest)
        return Data(digest).base64EncodedString()
    }
}