iOS开发中几种常见加解密方式

这篇文章主要介绍如下几种加密方式：

• base64
• md5
• AES
• RSA

在示例代码里面，没有专门写工具类，而是直接对NSString 写的分类，所有方法的调用直接采用[NSString xxxMethod]; 的形式。

好了，不废话，直接上代码。

---

base64加解密

1、加密过程：

NSString+EncryptVerbHandle.h 文件如下：

/**
 base64加密

 @param str 目标字符串
 @return 加密后的字符串
 */
+ (NSString *) base64EncodeFromString:(NSString *) str;

NSString+EncryptVerbHandle.m 文件如下：

+ (NSString *)base64EncodeFromString:(NSString *)str{
    //1、先将string转化为data二进制数据
    NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];
    //2、对二进制数据进行base64编码，返回编码后的字符串
    return [data base64EncodedStringWithOptions:0];
}

2、解密过程：

NSString+EncryptVerbHandle.h 文件如下：

/**
 base64解密

 @param str 目标字符串
 @return 解密后的字符串
 */
+ (NSString *) base64DecodeFromString:(NSString *) str;

NSString+EncryptVerbHandle.m 文件如下：

+ (NSString *)base64DecodeFromString:(NSString *)str{
    //1、先将base64编码后的字符串『解码』为二进制数据
    NSData *data = [[NSData alloc] initWithBase64EncodedString:str options:0];
    //2、把二进制数据转换为字符串返回
    return [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
}

---

MD5加密

由于md5无法解密（某些网站上的解密方法只是通过大型数据库的匹配比较来实现的），故本文只介绍加密过程。

NSString+EncryptVerbHandle.h 文件如下：

/**
 MD5加密算法
 MD5加密是单向的，只能加密不能解密.
 【MD5加密特点】：
 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。
 @param str 目标字符串
 @return md5加密后的字符串
 */
+ (NSString *) md5String:(NSString *) str;

NSString+EncryptVerbHandle.m 文件如下：

+ (NSString *)md5String:(NSString *)str{
    const char *cStr = [str UTF8String];
    unsigned char digest[CC_MD5_DIGEST_LENGTH];
    CC_MD5( cStr, (CC_LONG)strlen(cStr), digest);
    NSMutableString *output = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
    for(int i = 0; i < CC_MD5_DIGEST_LENGTH; i++)
        [output appendFormat:@"%02x", digest[i]];
    return  output;
}

---

AES加解密

1、加密过程：

NSString+EncryptVerbHandle.h 文件如下：

/**
 AES加密算法

 @param str 要加密的字符串
 @return 加密后的字符串
 */
+ (NSString *) aes256_encrypt:(NSString *) str;

NSString+EncryptVerbHandle.m 文件如下：

+ (NSString *)aes256_encrypt:(NSString *)str{
    char keyPtr[kCCKeySizeAES256 + 1];
    bzero(keyPtr, sizeof(keyPtr));
    /*AES加密与解密的秘钥，需要与后台协商共同定义，保持与后台的秘钥相同*/
    [AES_KEY getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    
    NSData *sourceData = [str dataUsingEncoding:NSUTF8StringEncoding];
    NSUInteger dataLength = [sourceData length];
    size_t buffersize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(buffersize);
    size_t numBytesEncrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding | kCCOptionECBMode, keyPtr, kCCBlockSizeAES128, NULL, [sourceData bytes], dataLength, buffer, buffersize, &numBytesEncrypted);
    
    if (cryptStatus == kCCSuccess) {
        NSData *encryptData = [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
        //对加密后的二进制数据进行base64转码
        return [encryptData base64EncodedStringWithOptions:NSDataBase64EncodingEndLineWithLineFeed];
    }else{
        free(buffer);
        return nil;
    }
}

2、解密过程：

NSString+EncryptVerbHandle.h 文件如下：

/**
 AES解密算法

 @param str 要解密的字符串
 @return 解密后的字符串
 */
+ (NSString *) aes256_decrypt:(NSString *) str;

NSString+EncryptVerbHandle.m 文件如下：

+ (NSString *)aes256_decrypt:(NSString *)str{
    //先对加密的字符串进行base64解码
    NSData *decodeData = [[NSData alloc] initWithBase64EncodedString:str options:NSDataBase64DecodingIgnoreUnknownCharacters];
    
    char keyPtr[kCCKeySizeAES256 + 1];
    bzero(keyPtr, sizeof(keyPtr));
    /*AES加密与解密的秘钥，需要与后台协商共同定义，保持与后台的秘钥相同*/
    [AES_KEY getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    
    NSUInteger dataLength = [decodeData length];
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    size_t numBytesDecrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding | kCCOptionECBMode, keyPtr, kCCBlockSizeAES128, NULL, [decodeData bytes], dataLength, buffer, bufferSize, &numBytesDecrypted);
    if (cryptStatus == kCCSuccess) {
        NSData *data = [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
        NSString *result = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        return result;
    }else{
        free(buffer);
        return nil;
    }
}

---

RSA加解密

【注意】采用公钥字符串加密和私钥字符串解密需要在工程中做如下设置：
TARGETS->Capabilities->Keychain Sharing-> 打开开关ON

Xcode工程设置

公钥字符串和私钥字符串可以在线生成

1、加密过程：

NSString+EncryptVerbHandle.h 文件如下：

/**
 *  RSA加密方法
 *
 *  @param str    需要加密的字符串
 *  @param pubKey 公钥字符串
 */
+ (NSString *)rsaEncryptString:(NSString *)str publicKey:(NSString *)pubKey;

NSString+EncryptVerbHandle.m 文件如下：

static NSString *base64_encode_data(NSData *data){
    data = [data base64EncodedDataWithOptions:0];
    NSString *ret = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    return ret;
}

#pragma mark - RSA公钥字符串加密，秘钥可以在http://web.chacuo.net/netrsakeypair里生成
+ (NSString *)rsaEncryptString:(NSString *)str publicKey:(NSString *)pubKey{
    NSData *data = [self encryptData:[str dataUsingEncoding:NSUTF8StringEncoding] publicKey:pubKey];
    NSString *ret = base64_encode_data(data);
    return ret;
}

+ (NSData *)encryptData:(NSData *)data publicKey:(NSString *)pubKey{
    if(!data || !pubKey){
        return nil;
    }
    SecKeyRef keyRef = [self addPublicKey:pubKey];
    if(!keyRef){
        return nil;
    }
    return [self encryptData:data withKeyRef:keyRef];
}

+ (SecKeyRef)addPublicKey:(NSString *)key{
    NSRange spos = [key rangeOfString:@"-----BEGIN PUBLIC KEY-----"];
    NSRange epos = [key rangeOfString:@"-----END PUBLIC KEY-----"];
    if(spos.location != NSNotFound && epos.location != NSNotFound){
        NSUInteger s = spos.location + spos.length;
        NSUInteger e = epos.location;
        NSRange range = NSMakeRange(s, e-s);
        key = [key substringWithRange:range];
    }
    key = [key stringByReplacingOccurrencesOfString:@"\r" withString:@""];
    key = [key stringByReplacingOccurrencesOfString:@"\n" withString:@""];
    key = [key stringByReplacingOccurrencesOfString:@"\t" withString:@""];
    key = [key stringByReplacingOccurrencesOfString:@" "  withString:@""];
    
    // This will be base64 encoded, decode it.
    NSData *data = base64_decode(key);
    data = [self stripPublicKeyHeader:data];
    if(!data){
        return nil;
    }
    
    //a tag to read/write keychain storage
    NSString *tag = @"RSAUtil_PubKey";
    NSData *d_tag = [NSData dataWithBytes:[tag UTF8String] length:[tag length]];
    
    // Delete any old lingering key with the same tag
    NSMutableDictionary *publicKey = [[NSMutableDictionary alloc] init];
    [publicKey setObject:(__bridge id) kSecClassKey forKey:(__bridge id)kSecClass];
    [publicKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
    [publicKey setObject:d_tag forKey:(__bridge id)kSecAttrApplicationTag];
    SecItemDelete((__bridge CFDictionaryRef)publicKey);
    
    // Add persistent version of the key to system keychain
    [publicKey setObject:data forKey:(__bridge id)kSecValueData];
    [publicKey setObject:(__bridge id) kSecAttrKeyClassPublic forKey:(__bridge id)
     kSecAttrKeyClass];
    [publicKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)
     kSecReturnPersistentRef];
    
    CFTypeRef persistKey = nil;
    OSStatus status = SecItemAdd((__bridge CFDictionaryRef)publicKey, &persistKey);
    if (persistKey != nil){
        CFRelease(persistKey);
    }
    if ((status != noErr) && (status != errSecDuplicateItem)) {
        return nil;
    }
    
    [publicKey removeObjectForKey:(__bridge id)kSecValueData];
    [publicKey removeObjectForKey:(__bridge id)kSecReturnPersistentRef];
    [publicKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)kSecReturnRef];
    [publicKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
    
    // Now fetch the SecKeyRef version of the key
    SecKeyRef keyRef = nil;
    status = SecItemCopyMatching((__bridge CFDictionaryRef)publicKey, (CFTypeRef *)&keyRef);
    if(status != noErr){
        return nil;
    }
    return keyRef;
}

+ (NSData *)stripPublicKeyHeader:(NSData *)d_key{
    // Skip ASN.1 public key header
    if (d_key == nil) return(nil);
    
    unsigned long len = [d_key length];
    if (!len) return(nil);
    
    unsigned char *c_key = (unsigned char *)[d_key bytes];
    unsigned int  idx     = 0;
    
    if (c_key[idx++] != 0x30) return(nil);
    
    if (c_key[idx] > 0x80) idx += c_key[idx] - 0x80 + 1;
    else idx++;
    
    // PKCS #1 rsaEncryption szOID_RSA_RSA
    static unsigned char seqiod[] =
    { 0x30,   0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01,
        0x01, 0x05, 0x00 };
    if (memcmp(&c_key[idx], seqiod, 15)) return(nil);
    
    idx += 15;
    
    if (c_key[idx++] != 0x03) return(nil);
    
    if (c_key[idx] > 0x80) idx += c_key[idx] - 0x80 + 1;
    else idx++;
    
    if (c_key[idx++] != '\0') return(nil);
    
    // Now make a new NSData from this buffer
    return ([NSData dataWithBytes:&c_key[idx] length:len - idx]);
}

+ (NSData *)encryptData:(NSData *)data withKeyRef:(SecKeyRef) keyRef{
    const uint8_t *srcbuf = (const uint8_t *)[data bytes];
    size_t srclen = (size_t)data.length;
    
    size_t block_size = SecKeyGetBlockSize(keyRef) * sizeof(uint8_t);
    void *outbuf = malloc(block_size);
    size_t src_block_size = block_size - 11;
    
    NSMutableData *ret = [[NSMutableData alloc] init];
    for(int idx=0; idx<srclen; idx+=src_block_size){
        //NSLog(@"%d/%d block_size: %d", idx, (int)srclen, (int)block_size);
        size_t data_len = srclen - idx;
        if(data_len > src_block_size){
            data_len = src_block_size;
        }
        
        size_t outlen = block_size;
        OSStatus status = noErr;
        status = SecKeyEncrypt(keyRef,
                               kSecPaddingPKCS1,
                               srcbuf + idx,
                               data_len,
                               outbuf,
                               &outlen
                               );
        if (status != 0) {
            NSLog(@"SecKeyEncrypt fail. Error Code: %d", status);
            ret = nil;
            break;
        }else{
            [ret appendBytes:outbuf length:outlen];
        }
    }
    
    free(outbuf);
    CFRelease(keyRef);
    return ret;
}

2、解密过程：

NSString+EncryptVerbHandle.h 文件如下：

/**
 *  RSA解密方法
 *
 *  @param str     需要解密的字符串
 *  @param privKey 私钥字符串
 */
+ (NSString *)rsaDecryptString:(NSString *)str privateKey:(NSString *)privKey;

NSString+EncryptVerbHandle.m 文件如下：

static NSData *base64_decode(NSString *str){
    NSData *data = [[NSData alloc] initWithBase64EncodedString:str options:NSDataBase64DecodingIgnoreUnknownCharacters];
    return data;
}

#pragma mark - RSA私钥字符串解密
+ (NSString *)rsaDecryptString:(NSString *)str privateKey:(NSString *)privKey{
    if (!str) return nil;
    NSData *data = [[NSData alloc] initWithBase64EncodedString:str options:0];
    data = [self decryptData:data privateKey:privKey];
    NSString *ret = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    return ret;
}

+ (NSData *)decryptData:(NSData *)data privateKey:(NSString *)privKey{
    if(!data || !privKey){
        return nil;
    }
    SecKeyRef keyRef = [self addPrivateKey:privKey];
    if(!keyRef){
        return nil;
    }
    return [self decryptData:data withKeyRef:keyRef];
}


+ (SecKeyRef)addPrivateKey:(NSString *)key{
    NSRange spos = [key rangeOfString:@"-----BEGIN RSA PRIVATE KEY-----"];
    NSRange epos = [key rangeOfString:@"-----END RSA PRIVATE KEY-----"];
    if(spos.location != NSNotFound && epos.location != NSNotFound){
        NSUInteger s = spos.location + spos.length;
        NSUInteger e = epos.location;
        NSRange range = NSMakeRange(s, e-s);
        key = [key substringWithRange:range];
    }
    key = [key stringByReplacingOccurrencesOfString:@"\r" withString:@""];
    key = [key stringByReplacingOccurrencesOfString:@"\n" withString:@""];
    key = [key stringByReplacingOccurrencesOfString:@"\t" withString:@""];
    key = [key stringByReplacingOccurrencesOfString:@" "  withString:@""];
    
    // This will be base64 encoded, decode it.
    NSData *data = base64_decode(key);
    data = [self stripPrivateKeyHeader:data];
    if(!data){
        return nil;
    }
    
    //a tag to read/write keychain storage
    NSString *tag = @"RSAUtil_PrivKey";
    NSData *d_tag = [NSData dataWithBytes:[tag UTF8String] length:[tag length]];
    
    // Delete any old lingering key with the same tag
    NSMutableDictionary *privateKey = [[NSMutableDictionary alloc] init];
    [privateKey setObject:(__bridge id) kSecClassKey forKey:(__bridge id)kSecClass];
    [privateKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
    [privateKey setObject:d_tag forKey:(__bridge id)kSecAttrApplicationTag];
    SecItemDelete((__bridge CFDictionaryRef)privateKey);
    
    // Add persistent version of the key to system keychain
    [privateKey setObject:data forKey:(__bridge id)kSecValueData];
    [privateKey setObject:(__bridge id) kSecAttrKeyClassPrivate forKey:(__bridge id)
     kSecAttrKeyClass];
    [privateKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)
     kSecReturnPersistentRef];
    
    CFTypeRef persistKey = nil;
    OSStatus status = SecItemAdd((__bridge CFDictionaryRef)privateKey, &persistKey);
    if (persistKey != nil){
        CFRelease(persistKey);
    }
    if ((status != noErr) && (status != errSecDuplicateItem)) {
        return nil;
    }
    
    [privateKey removeObjectForKey:(__bridge id)kSecValueData];
    [privateKey removeObjectForKey:(__bridge id)kSecReturnPersistentRef];
    [privateKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)kSecReturnRef];
    [privateKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
    
    // Now fetch the SecKeyRef version of the key
    SecKeyRef keyRef = nil;
    status = SecItemCopyMatching((__bridge CFDictionaryRef)privateKey, (CFTypeRef *)&keyRef);
    if(status != noErr){
        return nil;
    }
    return keyRef;
}

+ (NSData *)stripPrivateKeyHeader:(NSData *)d_key{
    // Skip ASN.1 private key header
    if (d_key == nil) return(nil);
    
    unsigned long len = [d_key length];
    if (!len) return(nil);
    
    unsigned char *c_key = (unsigned char *)[d_key bytes];
    unsigned int  idx     = 22; //magic byte at offset 22
    
    if (0x04 != c_key[idx++]) return nil;
    
    //calculate length of the key
    unsigned int c_len = c_key[idx++];
    int det = c_len & 0x80;
    if (!det) {
        c_len = c_len & 0x7f;
    } else {
        int byteCount = c_len & 0x7f;
        if (byteCount + idx > len) {
            //rsa length field longer than buffer
            return nil;
        }
        unsigned int accum = 0;
        unsigned char *ptr = &c_key[idx];
        idx += byteCount;
        while (byteCount) {
            accum = (accum << 8) + *ptr;
            ptr++;
            byteCount--;
        }
        c_len = accum;
    }
    
    // Now make a new NSData from this buffer
    return [d_key subdataWithRange:NSMakeRange(idx, c_len)];
}

+ (NSData *)decryptData:(NSData *)data withKeyRef:(SecKeyRef) keyRef{
    const uint8_t *srcbuf = (const uint8_t *)[data bytes];
    size_t srclen = (size_t)data.length;
    
    size_t block_size = SecKeyGetBlockSize(keyRef) * sizeof(uint8_t);
    UInt8 *outbuf = malloc(block_size);
    size_t src_block_size = block_size;
    
    NSMutableData *ret = [[NSMutableData alloc] init];
    for(int idx=0; idx<srclen; idx+=src_block_size){
        //NSLog(@"%d/%d block_size: %d", idx, (int)srclen, (int)block_size);
        size_t data_len = srclen - idx;
        if(data_len > src_block_size){
            data_len = src_block_size;
        }
        
        size_t outlen = block_size;
        OSStatus status = noErr;
        status = SecKeyDecrypt(keyRef,
                               kSecPaddingNone,
                               srcbuf + idx,
                               data_len,
                               outbuf,
                               &outlen
                               );
        if (status != 0) {
            NSLog(@"SecKeyEncrypt fail. Error Code: %d", status);
            ret = nil;
            break;
        }else{
            //the actual decrypted data is in the middle, locate it!
            int idxFirstZero = -1;
            int idxNextZero = (int)outlen;
            for ( int i = 0; i < outlen; i++ ) {
                if ( outbuf[i] == 0 ) {
                    if ( idxFirstZero < 0 ) {
                        idxFirstZero = i;
                    } else {
                        idxNextZero = i;
                        break;
                    }
                }
            }
            
            [ret appendBytes:&outbuf[idxFirstZero+1] length:idxNextZero-idxFirstZero-1];
        }
    }
    
    free(outbuf);
    CFRelease(keyRef);
    return ret;
}