常见加密算法

1、MD5   
//因为是使用category，所以木有参数传入啦

-(NSString *) stringFromMD5 {
    if(self == nil || [self length] == 0) {
        return nil;
    }
    const char *value = [self UTF8String];
    unsigned char outputBuffer[CC_MD5_DIGEST_LENGTH];
    CC_MD5(value, strlen(value), outputBuffer);
    NSMutableString *outputString = [[NSMutableString alloc] initWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
    for(NSInteger count = 0; count < CC_MD5_DIGEST_LENGTH; count++){
        [outputString appendFormat:@"%02x",outputBuffer[count]];
    }
    return [outputString autorelease];
}


2、Base64

+ (NSString *) base64EncodeData: (NSData *) objData {
const unsigned char * objRawData = [objData bytes];
char * objPointer;
char * strResult;

// Get the Raw Data length and ensure we actually have data
int intLength = [objData length];
if (intLength == 0) return nil;

// Setup the String-based Result placeholder and pointer within that placeholder
strResult = (char *)calloc(((intLength + 2) / 3) * 4, sizeof(char));
objPointer = strResult;

// Iterate through everything
while (intLength > 2) { // keep going until we have less than 24 bits
*objPointer++ = _base64EncodingTable[objRawData[0] >> 2];
*objPointer++ = _base64EncodingTable[((objRawData[0] & 0x03) << 4) + (objRawData[1] >> 4)];
*objPointer++ = _base64EncodingTable[((objRawData[1] & 0x0f) << 2) + (objRawData[2] >> 6)];
*objPointer++ = _base64EncodingTable[objRawData[2] & 0x3f];

// we just handled 3 octets (24 bits) of data
objRawData += 3;
intLength -= 3;
}

// now deal with the tail end of things
if (intLength != 0) {
*objPointer++ = _base64EncodingTable[objRawData[0] >> 2];
if (intLength > 1) {
*objPointer++ = _base64EncodingTable[((objRawData[0] & 0x03) << 4) + (objRawData[1] >> 4)];
*objPointer++ = _base64EncodingTable[(objRawData[1] & 0x0f) << 2];
*objPointer++ = '=';
} else {
*objPointer++ = _base64EncodingTable[(objRawData[0] & 0x03) << 4];
*objPointer++ = '=';
*objPointer++ = '=';
}
}

// Terminate the string-based result
*objPointer = '';

    NSString *rstStr = [NSString stringWithCString:strResult encoding:NSASCIIStringEncoding];
    free(objPointer);
    return rstStr;
}




3、AES
-(NSData*) EncryptAES: (NSString *) key {
    char keyPtr[kCCKeySizeAES256+1];
    bzero(keyPtr, sizeof(keyPtr));

    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];

    NSUInteger dataLength = [self length];

    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);

    size_t numBytesEncrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128,
                                          kCCOptionPKCS7Padding | kCCOptionECBMode,
                                          keyPtr, kCCBlockSizeAES128,
                                          NULL,
                                          [self bytes], dataLength,
                                          buffer, bufferSize,
                                          &numBytesEncrypted);
    if (cryptStatus == kCCSuccess) {
        return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
    }

    free(buffer);
    return nil;
}


4、RSA

- (NSData *) encryptWithData:(NSData *)content {
    size_t plainLen = [content length];
    if (plainLen > maxPlainLen) {
        NSLog(@"content(%ld) is too long, must < %ld", plainLen, maxPlainLen);
        return nil;
    }

    void *plain = malloc(plainLen);
    [content getBytes:plain
               length:plainLen];

    size_t cipherLen = 128; // currently RSA key length is set to 128 bytes
    void *cipher = malloc(cipherLen);

    OSStatus returnCode = SecKeyEncrypt(publicKey, kSecPaddingPKCS1, plain,
                                        plainLen, cipher, &cipherLen);

    NSData *result = nil;
    if (returnCode != 0) {
        NSLog(@"SecKeyEncrypt fail. Error Code: %ld", returnCode);
    }
    else {
        result = [NSData dataWithBytes:cipher
                                length:cipherLen];
    }

    free(plain);
    free(cipher);

    return result;
}