1 通过简单的URLENCODE ＋ BASE64编码防止数据明文传输
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。
3 对于重要数据，使用RSA进行数字签名，起到防篡改作用。
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] == ) {
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 = ; count < CC_MD5_DIGEST_LENGTH; count ){
[outputString appendFormat:@"x",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 == ) 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[] >> 2];
objPointer = _base64EncodingTable[((objRawData[] & 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 != ) {
objPointer = _base64EncodingTable[objRawData[] >> 2];
if (intLength > 1) {
objPointer = _base64EncodingTable[((objRawData[] & 0x03) << 4) (objRawData[1] >> 4)];
objPointer = _base64EncodingTable[(objRawData[1] & 0x0f) << 2];
objPointer = '=';
} else {
objPointer = _base64EncodingTable[(objRawData[] & 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 = ;
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 != ) {
NSLog(@"SecKeyEncrypt fail. Error Code: %ld", returnCode);
}
else {
result = [NSData dataWithBytes:cipher
length:cipherLen];
}
free(plain);
free(cipher);
return result;
}
