iOS 常用的加密技术-MD5,DES,AES

网络请求中为了数据的安全性 , 通常会对数据进行加密之后再以JSON形式传输到后台 . 就算请求被拦截 , 也可以有效的保护用户信息的安全性 . 今天就分享一下 常用的一些加密技术 .

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MD5 加密

MD5是利用哈希算法来加密的。哈希算法是一种摘要算法，MD5有以下两个最主要的特性 , 常用于用户密码的加密使用。

• 加密的不可逆性，只能够加密，不能够解密。
• 任意长度的明文经过加密后长度都是固定的，长度为16进制32位。

使用MD5 加密之前应该先导入框架 #import "CommonCrypto/CommonDigest.h"

// MD5 转码
-(NSString *) md5: (NSString *) inPutText
{
    const char *cStr = [inPutText UTF8String];
    unsigned char result[CC_MD5_DIGEST_LENGTH];
    CC_MD5(cStr, (CC_LONG)strlen(cStr), result);
    
    return [[NSString stringWithFormat:@"%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X",
             result[0], result[1], result[2], result[3],
             result[4], result[5], result[6], result[7],
             result[8], result[9], result[10], result[11],
             result[12], result[13], result[14], result[15]
             ] lowercaseString];
}

DES加密

DES 加密是一种对称式加密方法 . 其特点是

• 加密与解密使用同一套** , 使用方便 .
• 具有相当高的复杂性, 其安全性仅以加***的保密为基础 .

与MD5 一样也需要导入框架#import "CommonCrypto/CommonDigest.h"
然后还要导入GTMBase64文件

//加密
+(NSString *)decryptWithContent:(NSString *)content
{
    //** "abc123"
    char * keyChar =(char*)[@"abc123" UTF8String];
    
    if (content == nil) {
        content = @"";
    }
    
    NSString *jm = [NSString stringWithCString:encryptWithKeyAndType([content UTF8String], kCCEncrypt, keyChar) encoding:NSUTF8StringEncoding];
    
    return jm;
    
}

//解密
+ (NSData *)encryptWithContent:(NSData *)content
{
    NSString *contentStr = [[NSString alloc] initWithData:content encoding:NSUTF8StringEncoding];
    
    if (contentStr == nil || [contentStr isEqualToString:@""]) {
        return nil;
    }
    
    const char * contentChar =[contentStr UTF8String];
    //** "abc123"
    char * keyChar =(char*)[@"abc123" UTF8String];
    const char *miChar;
    miChar = encryptWithKeyAndType(contentChar, kCCDecrypt, keyChar);
    if (miChar == nil) {
        miChar = "";
    }
    
    NSString *zmStr = [NSString stringWithCString:miChar encoding:NSUTF8StringEncoding];
    if (zmStr == nil) {
        zmStr [email protected]"";
    }
    return [zmStr dataUsingEncoding:NSUTF8StringEncoding];
}

//核心代码
static const char* encryptWithKeyAndType(const char *text,CCOperation encryptOperation,char *key)
{
    NSString *textString=[[NSString alloc]initWithCString:text encoding:NSUTF8StringEncoding];
    //      NSLog(@"[[item.url description] UTF8String=%@",textString);
    const void *dataIn;
    size_t dataInLength;
    
    if (encryptOperation == kCCDecrypt)//传递过来的是decrypt 解码
    {
        //解码 base64
        NSData *decryptData = [GTMBase64 decodeData:[textString dataUsingEncoding:NSUTF8StringEncoding]];//转成utf-8并decode
        dataInLength = [decryptData length];
        dataIn = [decryptData bytes];
    }
    else  //encrypt
    {
        NSData* encryptData = [textString dataUsingEncoding:NSUTF8StringEncoding];
        dataInLength = [encryptData length];
        dataIn = (const void *)[encryptData bytes];
    }
    
    
    CCCryptorStatus ccStatus;
    uint8_t *dataOut = NULL; //可以理解位type/typedef 的缩写（有效的维护了代码，比如：一个人用int，一个人用long。最好用typedef来定义）
    size_t dataOutAvailable = 0; //size_t  是操作符sizeof返回的结果类型
    size_t dataOutMoved = 0;
    
    dataOutAvailable = (dataInLength + kCCBlockSizeDES) & ~(kCCBlockSizeDES - 1);
    dataOut = malloc( dataOutAvailable * sizeof(uint8_t));
    memset((void *)dataOut, 00, dataOutAvailable);//将已开辟内存空间buffer的首 1 个字节的值设为值 0
    
    //NSString *initIv = @"12345678";
    const void *vkey = key;
    const void *iv = (const void *) key; //[initIv UTF8String];
    
    //CCCrypt函数 加密/解密
    ccStatus = CCCrypt(encryptOperation,//  加密/解密
                       kCCAlgorithmDES,//  加密根据哪个标准（des，3des，aes。。。。）
                       kCCOptionPKCS7Padding,//  选项分组密码算法(des:对每块分组加一次密  3DES：对每块分组加三个不同的密)
                       vkey,  //**    加密和解密的**必须一致
                       kCCKeySizeDES,//   DES **的大小（kCCKeySizeDES=8）
                       iv, //  可选的初始矢量
                       dataIn, // 数据的存储单元
                       dataInLength,// 数据的大小
                       (void *)dataOut,// 用于返回数据
                       dataOutAvailable,
                       &dataOutMoved);
    
    NSString *result = nil;
    
    if (encryptOperation == kCCDecrypt)//encryptOperation==1  解码
    {
        //得到解密出来的data数据，改变为utf-8的字符串
        result = [[NSString alloc] initWithData:[NSData dataWithBytes:(const void *)dataOut length:(NSUInteger)dataOutMoved] encoding:NSUTF8StringEncoding];
    }
    else //encryptOperation==0  （加密过程中，把加好密的数据转成base64的）
    {
        //编码 base64
        NSData *data = [NSData dataWithBytes:(const void *)dataOut length:(NSUInteger)dataOutMoved];
        result = [GTMBase64 stringByEncodingData:data];
    }
    
    return [result UTF8String];
    
}

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AES加密

AES加密是一种更高级的对称加密算法 . 其特点是

• **为128位(也有192-256的变体) , 相比DES(56位)更安全.
• 隐藏了明文模式 , 分组密码转化为流模式

先导入框架 #import <CommonCrypto/CommonCryptor.h>
代码下载地址

//加密
- (NSData *)AES256EncryptWithKey:(NSString *)key {
    // 'key' should be 32 bytes for AES256, will be null-padded otherwise
    char keyPtr[kCCKeySizeAES256+1]; // room for terminator (unused)
    bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)
    
    // fetch key data
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    
    NSUInteger dataLength = [self length];
    
    //See the doc: For block ciphers, the output size will always be less than or
    //equal to the input size plus the size of one block.
    //That's why we need to add the size of one block here
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    
    size_t numBytesEncrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt,
                                          kCCAlgorithmAES128,
                                          kCCOptionPKCS7Padding,
                                          keyPtr, kCCKeySizeAES256,
                                          NULL /* initialization vector (optional) */,
                                          [self bytes], dataLength, /* input */
                                          buffer, bufferSize, /* output */
                                          &numBytesEncrypted);
    if (cryptStatus == kCCSuccess) {
        //the returned NSData takes ownership of the buffer and will free it on deallocation
        return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
    }
    
    free(buffer); //free the buffer;
    return nil;
}

//解密
- (NSData *)AES256DecryptWithKey:(NSString *)key {
    // 'key' should be 32 bytes for AES256, will be null-padded otherwise
    char keyPtr[kCCKeySizeAES256+1]; // room for terminator (unused)
    bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)
    
    // fetch key data
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    
    NSUInteger dataLength = [self length];
    
    //See the doc: For block ciphers, the output size will always be less than or
    //equal to the input size plus the size of one block.
    //That's why we need to add the size of one block here
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    
    size_t numBytesDecrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                          keyPtr, kCCKeySizeAES256,
                                          NULL /* initialization vector (optional) */,
                                          [self bytes], dataLength, /* input */
                                          buffer, bufferSize, /* output */
                                          &numBytesDecrypted);
    
    if (cryptStatus == kCCSuccess) {
        //the returned NSData takes ownership of the buffer and will free it on deallocation
        return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
    }
    
    free(buffer); //free the buffer;
    return nil;
}

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