（1）首先创建桥接头文件bridge.h来包含需要引用的Objective-C头文件，并在项目中配置

#import <CommonCrypto/CommonHMAC.h>

（2）下面是一个封装类，同时对String进行扩展。（除了SHA1，还可以使用其它算法比如MD5，SHA224等）

//HMAC.swift
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 { var md5: String! { let str = self.cStringUsingEncoding(NSUTF8StringEncoding) let strLen = CC_LONG(self.lengthOfBytesUsingEncoding(NSUTF8StringEncoding)) let digestLen = Int(CC_MD5_DIGEST_LENGTH) let result = UnsafeMutablePointer<CUnsignedChar>.alloc(digestLen) CC_MD5(str!,strLen,result) return stringFromBytes(result,length: digestLen) } var sha1: String! { let str = self.cStringUsingEncoding(NSUTF8StringEncoding) let strLen = CC_LONG(self.lengthOfBytesUsingEncoding(NSUTF8StringEncoding)) let digestLen = Int(CC_SHA1_DIGEST_LENGTH) let result = UnsafeMutablePointer<CUnsignedChar>.alloc(digestLen) CC_SHA1(str!,length: digestLen) } var sha256String: String! { let str = self.cStringUsingEncoding(NSUTF8StringEncoding) let strLen = CC_LONG(self.lengthOfBytesUsingEncoding(NSUTF8StringEncoding)) let digestLen = Int(CC_SHA256_DIGEST_LENGTH) let result = UnsafeMutablePointer<CUnsignedChar>.alloc(digestLen) CC_SHA256(str!,length: digestLen) } var sha512String: String! { let str = self.cStringUsingEncoding(NSUTF8StringEncoding) let strLen = CC_LONG(self.lengthOfBytesUsingEncoding(NSUTF8StringEncoding)) let digestLen = Int(CC_SHA512_DIGEST_LENGTH) let result = UnsafeMutablePointer<CUnsignedChar>.alloc(digestLen) CC_SHA512(str!,length: digestLen) } func stringFromBytes(bytes: UnsafeMutablePointer<CUnsignedChar>,length: Int) -> String{ let hash = NSMutableString() for i in 0..<length { hash.appendFormat("%02x",bytes[i]) } bytes.dealloc(length) return String(format: hash as String) } func hmac(algorithm: CryptoAlgorithm,key: String) -> String { let str = self.cStringUsingEncoding(NSUTF8StringEncoding) let strLen = Int(self.lengthOfBytesUsingEncoding(NSUTF8StringEncoding)) let digestLen = algorithm.digestLength let result = UnsafeMutablePointer<CUnsignedChar>.alloc(digestLen) let keyStr = key.cStringUsingEncoding(NSUTF8StringEncoding) let keyLen = Int(key.lengthOfBytesUsingEncoding(NSUTF8StringEncoding)) CCHmac(algorithm.HMACAlgorithm,keyStr!,keyLen,str!,result) let digest = stringFromResult(result,length: digestLen) result.dealloc(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) } }

（3）测试样例

let str = "welcome to hangge.com"
let key = "67FG"
let hmacStr = str.hmac(.SHA1,key: key)
let pwd = str.d5

print("原始字符串：\(str)")
print("key：\(key)")
print("HMAC运算结果：\(hmacStr)")
print("md5运算结果：\(pwd)")

/**** 输出 ****** 原始字符串：welcome to hangge.com key：67FG HMAC运算结果：79a5f5b138b5646289a9648de035c80e9c5c14c7 md5运算结果：0d5ca19da68a37af5900c8ebf5356c6e *****/