今天就跟大家分享一下IOS常用加密算法,如果有错误的地方,还希望大家帮忙更正哈~

先说一下我们游戏设计时候的安全考虑吧(懒得打字,直接从设计文档中复制了,还请见谅….自己的独立游戏,所以100%的版权哈)

5.1 通过简单的URLENCODE + BASE64编码防止数据明文传输

5.2 对普通请求、返回数据,生成MD5校验(MD5中加入动态密钥),进行数据完整性(简单防篡改,安全性较低,优点:快速)校验。

5.3 对于重要数据,使用RSA进行数字签名,起到防篡改作用。

5.4 对于比较敏感的数据,如用户信息(登陆、注册等),客户端发送使用RSA加密,服务器返回使用DES(AES)加密。

原因:客户端发送之所以使用RSA加密,是因为RSA解密需要知道服务器私钥,而服务器私钥一般盗取难度较大;如果使用DES的话,可以通过破解客户端获取密钥,安全性较低。而服务器返回之所以使用DES,是因为不管使用DES还是RSA,密钥(或私钥)都存储在客户端,都存在被破解的风险,因此,需要采用动态密钥,而RSA的密钥生成比较复杂,不太适合动态密钥,并且RSA速度相对较慢,所以选用DES)

把相关算法的代码也贴一下吧 (其实使用一些成熟的第三方库或许会来得更加简单,不过自己写,自由点)。注,这里的大部分加密算法都是参考一些现有成熟的算法,或者直接拿来用的。

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 = '\0';

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;

}