然后写一个生成md5的函数：

class func md5String(str:String) ->String{

var cStr = (stras NSString).UTF8String

var buffer =UnsafeMutablePointer<UInt8>.alloc(16)

CC_MD5(cStr,(CC_LONG)(strlen(cStr)),buffer)

var md5String:NSMutableString =NSMutableString();

forvar i = 0; i <16; ++i{

md5String.appendFormat("%X2",buffer)

}

free(buffer)

returnString(md5String);

}