參考鏈接：http://www.2cto.com/kf/201502/375348.html
最近在面試，一直問到加密策吠，發(fā)現(xiàn)答案不是對方想要的脾还，肯定是我少學了幾種性锭，于是進行百度，發(fā)現(xiàn)在我的iOS職業(yè)生涯確實少了一種加密：RSA加密涉兽。
以下是常用的加密算法介紹：
先說一下我們游戲設計時候的安全考慮吧（懶得打字招驴，直接從設計文檔中復制了，還請見諒....自己的獨立游戲枷畏，所以100%的版權哈）
1 通過簡單的URLENCODE ＋ BASE64編碼防止數(shù)據(jù)明文傳輸
2 對普通請求别厘、返回數(shù)據(jù)，生成MD5校驗（MD5中加入動態(tài)密鑰）矿辽，進行數(shù)據(jù)完整性（簡單防篡改丹允，安全性較低，優(yōu)點：快速）校驗袋倔。
3 對于重要數(shù)據(jù)雕蔽，使用RSA進行數(shù)字簽名，起到防篡改作用宾娜。
4 對于比較敏感的數(shù)據(jù)批狐，如用戶信息（登陸、注冊等）前塔，客戶端發(fā)送使用RSA加密嚣艇，服務器返回使用DES(AES)加密。
原因：客戶端發(fā)送之所以使用RSA加密华弓，是因為RSA解密需要知道服務器私鑰食零，而服務器私鑰一般盜取難度較大；如果使用DES的話寂屏，可以通過破解客戶端獲取密鑰贰谣，安全性較低。而服務器返回之所以使用DES迁霎，是因為不管使用DES還是RSA吱抚，密鑰（或私鑰）都存儲在客戶端，都存在被破解的風險考廉，因此秘豹，需要采用動態(tài)密鑰，而RSA的密鑰生成比較復雜昌粤，不太適合動態(tài)密鑰既绕，并且RSA速度相對較慢啄刹，所以選用DES）
把相關算法的代碼也貼一下吧 （其實使用一些成熟的第三方庫或許會來得更加簡單，不過自己寫岸更，自由點）鸵膏。注，這里的大部分加密算法都是參考一些現(xiàn)有成熟的算法怎炊，或者直接拿來用的谭企。
1、MD5
//因為是使用category评肆，所以木有參數(shù)傳入啦
-(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债查、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瓜挽、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;
}
