IOS 杂笔－9 （MD5 加密）

首先是一段对MD5的简介

＊出自一位大牛之手＊

Message Digest Algorithm MD5（中文名为消息摘要算法第五版）为计算机安全领域广泛使用的一种散列函数，用以提供消息的完整性保护

是计算机广泛使用的杂凑算法之一（又译摘要算法、哈希算法），主流编程语言普遍已有MD5实现。

MD5算法具有以下特点：

1、压缩性：任意长度的数据，算出的MD5值长度都是固定的。

2、容易计算：从原数据计算出MD5值很容易。

3、抗修改性：对原数据进行任何改动，哪怕只修改1个字节，所得到的MD5值都有很大区别。

4、强抗碰撞：已知原数据和其MD5值，想找到一个具有相同MD5值的数据（即伪造数据）是非常困难的。

MD5的作用是让大容量信息在用数字签名软件签署私人密钥前被"压缩"成一种保密的格式（就是把一个任意长度的字节串变换成一定长的十六进制数字串）。除了MD5以外，其中比较有名的还有sha-1、RIPEMD以及Haval等。

//
//  ViewController.m
//  CX－MD5加密
//
//  Created by xubaoaichiyu on 16/3/22.
//  Copyright © 2016年 大xubaoaichiyu. All rights reserved.
//

#import "ViewController.h"
#import "NSString+Hash.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    NSString * password = @"xubaoaichiyu";

    NSLog(@"%@",password.md5String);

    //md5加盐
    NSString * repassword = [password stringByAppendingString:@"love"];

    NSLog(@"%@",repassword.md5String);
}

@end

MD5 可以说是用c语言编程，但是对于喜欢面向对象的我们当然会有三方实现。通过这个三方我门可以很方便的解决繁重的c语言代码上。下面是三方的.h.m文件。

//
//  NSString+Hash.h
//
//  Created by Tom Corwine on 5/30/12..
//

#import <Foundation/Foundation.h>

@interface NSString (Hash)

@property (readonly) NSString *md5String;
@property (readonly) NSString *sha1String;
@property (readonly) NSString *sha256String;
@property (readonly) NSString *sha512String;

- (NSString *)hmacSHA1StringWithKey:(NSString *)key;
- (NSString *)hmacSHA256StringWithKey:(NSString *)key;
- (NSString *)hmacSHA512StringWithKey:(NSString *)key;

@end

//
//  NSString+Hash.m
//
//  Created by Tom Corwine on 5/30/12.
//

#import "NSString+hash.h"

#import <CommonCrypto/CommonDigest.h>
#import <CommonCrypto/CommonHMAC.h>

@implementation NSString (Hash)

- (NSString *)md5String
{
    const char *string = self.UTF8String;
    int length = (int)strlen(string);
    unsigned char bytes[CC_MD5_DIGEST_LENGTH];
    CC_MD5(string, length, bytes);
    return [self stringFromBytes:bytes length:CC_MD5_DIGEST_LENGTH];
}

- (NSString *)sha1String
{
    const char *string = self.UTF8String;
    int length = (int)strlen(string);
    unsigned char bytes[CC_SHA1_DIGEST_LENGTH];
    CC_SHA1(string, length, bytes);
    return [self stringFromBytes:bytes length:CC_SHA1_DIGEST_LENGTH];
}

- (NSString *)sha256String
{
    const char *string = self.UTF8String;
    int length = (int)strlen(string);
    unsigned char bytes[CC_SHA256_DIGEST_LENGTH];
    CC_SHA256(string, length, bytes);
    return [self stringFromBytes:bytes length:CC_SHA256_DIGEST_LENGTH];
}

- (NSString *)sha512String
{
    const char *string = self.UTF8String;
    int length = (int)strlen(string);
    unsigned char bytes[CC_SHA512_DIGEST_LENGTH];
    CC_SHA512(string, length, bytes);
    return [self stringFromBytes:bytes length:CC_SHA512_DIGEST_LENGTH];
}

- (NSString *)hmacSHA1StringWithKey:(NSString *)key
{
    NSData *keyData = [key dataUsingEncoding:NSUTF8StringEncoding];
    NSData *messageData = [self dataUsingEncoding:NSUTF8StringEncoding];
    NSMutableData *mutableData = [NSMutableData dataWithLength:CC_SHA1_DIGEST_LENGTH];
    CCHmac(kCCHmacAlgSHA1, keyData.bytes, keyData.length, messageData.bytes, messageData.length, mutableData.mutableBytes);
    return [self stringFromBytes:(unsigned char *)mutableData.bytes length:mutableData.length];
}

- (NSString *)hmacSHA256StringWithKey:(NSString *)key
{
    NSData *keyData = [key dataUsingEncoding:NSUTF8StringEncoding];
    NSData *messageData = [self dataUsingEncoding:NSUTF8StringEncoding];
    NSMutableData *mutableData = [NSMutableData dataWithLength:CC_SHA256_DIGEST_LENGTH];
    CCHmac(kCCHmacAlgSHA256, keyData.bytes, keyData.length, messageData.bytes, messageData.length, mutableData.mutableBytes);
    return [self stringFromBytes:(unsigned char *)mutableData.bytes length:mutableData.length];
}

- (NSString *)hmacSHA512StringWithKey:(NSString *)key
{
    NSData *keyData = [key dataUsingEncoding:NSUTF8StringEncoding];
    NSData *messageData = [self dataUsingEncoding:NSUTF8StringEncoding];
    NSMutableData *mutableData = [NSMutableData dataWithLength:CC_SHA512_DIGEST_LENGTH];
    CCHmac(kCCHmacAlgSHA512, keyData.bytes, keyData.length, messageData.bytes, messageData.length, mutableData.mutableBytes);
    return [self stringFromBytes:(unsigned char *)mutableData.bytes length:mutableData.length];
}

#pragma mark - Helpers

- (NSString *)stringFromBytes:(unsigned char *)bytes length:(int)length
{
    NSMutableString *mutableString = @"".mutableCopy;
    for (int i = ; i < length; i++)
        [mutableString appendFormat:@"%02x", bytes[i]];
    return [NSString stringWithString:mutableString];
}

@end