Easy to use Swift implementation of CommonCrypto HMAC. You can easily hash your String to: md5, sha1, sha224, sha256, sha384, sha512 with pure Swift.

HMAC.swift

//
//  HMAC.swift
//
//  Created by Mihael Isaev on 21.04.15.
//  Copyright (c) 2014 Mihael Isaev inc. All rights reserved.
//
// ***********************************************************
//
// How to import CommonCrypto in Swift project without Obj-c briging header
//
// To work around this create a directory called CommonCrypto in the root of the project using Finder.
// In this directory create a file name module.map and copy the following into the file.
// You will need to alter the paths to ensure they point to the headers on your system.
//
// module CommonCrypto [system] {
//     header "/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/include/CommonCrypto/CommonCrypto.h"
//     export *
// }
// To make this module visible to Xcode, go to Build Settings, Swift Compiler – Search Paths
// and set Import Paths to point to the directory that contains the CommonCrypto directory.
//
// You should now be able to use import CommonCrypto in your Swift code.
//
// You have to set the Import Paths in every project that uses your framework so that Xcode can find it.
//
// ***********************************************************
//

import Foundation
import CommonCrypto

extension String {
    var md5: String {
        return HMAC.hash(self, algo: HMACAlgo.MD5)
    }
    
    var sha1: String {
        return HMAC.hash(self, algo: HMACAlgo.SHA1)
    }
    
    var sha224: String {
        return HMAC.hash(self, algo: HMACAlgo.SHA224)
    }
    
    var sha256: String {
        return HMAC.hash(self, algo: HMACAlgo.SHA256)
    }
    
    var sha384: String {
        return HMAC.hash(self, algo: HMACAlgo.SHA384)
    }
    
    var sha512: String {
        return HMAC.hash(self, algo: HMACAlgo.SHA512)
    }
}

public struct HMAC {
    
    static func hash(inp: String, algo: HMACAlgo) -> String {
        if let stringData = inp.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false) {
            return hexStringFromData(digest(stringData, algo: algo))
        }
        return ""
    }
    
    private static func digest(input : NSData, algo: HMACAlgo) -> NSData {
        let digestLength = algo.digestLength()
        var hash = [UInt8](count: digestLength, repeatedValue: 0)
        switch algo {
        case .MD5:
            CC_MD5(input.bytes, UInt32(input.length), &hash)
            break
        case .SHA1:
            CC_SHA1(input.bytes, UInt32(input.length), &hash)
            break
        case .SHA224:
            CC_SHA224(input.bytes, UInt32(input.length), &hash)
            break
        case .SHA256:
            CC_SHA256(input.bytes, UInt32(input.length), &hash)
            break
        case .SHA384:
            CC_SHA384(input.bytes, UInt32(input.length), &hash)
            break
        case .SHA512:
            CC_SHA512(input.bytes, UInt32(input.length), &hash)
            break
        }
        return NSData(bytes: hash, length: digestLength)
    }
    
    private static func hexStringFromData(input: NSData) -> String {
        var bytes = [UInt8](count: input.length, repeatedValue: 0)
        input.getBytes(&bytes, length: input.length)
        
        var hexString = ""
        for byte in bytes {
            hexString += String(format:"%02x", UInt8(byte))
        }
        
        return hexString
    }
}

enum HMACAlgo {
    case MD5, SHA1, SHA224, SHA256, SHA384, SHA512
    
    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)
    }
}