Base64 encode a XXTEA encrypted string error

Question

I would like to secure my data so I try to encrypt it with XXTEA. I do this way:

inputString -> XXTEA encrypt -> outputString
outputString -> XXTEA decrypt -> inputString

Everything is encrypt and decrypt ok. But when I try to make a base64 encode the output after XXTEA encrypt it and base64 decode it before XXTEA decrypt, the result is wrong:

input -> XXTEA encrypt -> base64 encode -> output
output -> base64 decode -> XXTEA decrypt != input

When I test with http://www.tools4noobs.com/online_tools/xxtea_encrypt/ and http://www.tools4noobs.com/online_tools/xxtea_decrypt/

My example's input string is hello and its final result is bjz/S2f3Xkxr08hu

But when I test with my code (see below), the final result is bjz/Sw==

Here is my encryption code:

std::string ProjectUtils::encrypt_data_xxtea(std::string input, std::string secret) {
//Encrypt with XXTEA
xxtea_long retLength = 0;

unsigned char data[input.length()];
strncpy((char*)data, input.c_str(), sizeof(data));
xxtea_long dataLength = (xxtea_long) sizeof(data);

unsigned char key[secret.length()];
strncpy((char*)key, secret.c_str(), sizeof(key));
xxtea_long keyLength = (xxtea_long) sizeof(key);

unsigned char *encryptedData = xxtea_encrypt(data, dataLength, key, keyLength, &retLength);

//Encode base64
char* out = NULL;
base64Encode(encryptedData, sizeof(encryptedData), &out);

CCLOG("xxtea encrypted data: %s", out);
return out;

}

Here is my decryption code:

char* ProjectUtils::decrypt_data_xxtea(std::string input, std::string secret) {
//Decode base64
unsigned char* output = NULL;
base64Decode((unsigned char*)input.c_str(), (unsigned int)strlen(input.c_str()), &output);
xxtea_long dataLength = (xxtea_long) sizeof(output);

xxtea_long retLength = 0;

unsigned char key[secret.length()];
strncpy((char*)key, secret.c_str(), sizeof(key));
xxtea_long keyLength = (xxtea_long) sizeof(key);

//Decrypt with XXTEA
char *decryptedData = reinterpret_cast<char*>(xxtea_decrypt(output, dataLength, key, keyLength, &retLength));

CCLOG("xxtea decrypted data: %s", decryptedData);
return decryptedData;

}

Do you know what is wrong with my code? Any help would be appreciated! Thanks very much.

I encode base64 after encrypt it with xxtea because the result when encrypt with xxtea has special character like **©ʱL\327_1xA\344R**, and I cannot save it into userdefault. Is there any way to convert a string has special character to normal format? — Nikel Arteta, Mar 20 '15 at 08:47

score 1 · Accepted Answer · answered Jun 16 '15 at 07:45

here is full working code on cocos2d-x 3.4

std::string UserProfile::encryptString(std::string input, std::string secret) {
    //Encrypt with XXTEA
    xxtea_long retLength = 0;

    unsigned char data[input.length()];
    strncpy((char*)data, input.c_str(), sizeof(data));
    xxtea_long dataLength = (xxtea_long) sizeof(data);

    unsigned char key[secret.length()];
    strncpy((char*)key, secret.c_str(), sizeof(key));
    xxtea_long keyLength = (xxtea_long) sizeof(key);

    unsigned const char *encryptedData = reinterpret_cast<unsigned const char*>(xxtea_encrypt(data, dataLength, key, keyLength, &retLength));

    char* out = NULL;
    cocos2d::base64Encode(encryptedData, retLength, &out); // use real length returned by xxtea_encrypt
    CCLOG("xxtea encrypted data: [%s][%s]", encryptedData, out);


    std::string outStr(out); // make string object
    CCLOG("xxtea encrypted data: [%s][%s]", encryptedData, outStr.c_str());


    setStr(KEY, outStr); // function that store value in user defaults


    std::string revertStr = getStr(KEY); // get string value back
    CCLOG("xxtea revertStr: [%s]", revertStr.c_str());

    unsigned char* output = NULL;
    int outLength = cocos2d::base64Decode((unsigned char*)revertStr.c_str(), (unsigned int)strlen(revertStr.c_str()), &output); // get real length of decoded string
    char *decryptedData = reinterpret_cast<char*>(xxtea_decrypt(output, outLength, key, keyLength, &retLength)); // use it

    CCLOG("xxtea decrypted data: %s", decryptedData); // string the same as original for me

    return "";
}

Could you please elaborate more your answer adding a little more description about the solution you provide? — abarisone, Jun 16 '15 at 08:14

Alex Gongalsky · Answer 2 · 2015-06-16T07:38:41.597

0

thanks for your code, it works for me)

I have replaced length of base64 string by actual retLength

base64Encode(encryptedData, retLength, &out);

and back, get actual size as well

int outLength = cocos2d::base64Decode((unsigned char*)revertStr.c_str(), (unsigned int)strlen(revertStr.c_str()), &output);
char *decryptedData = reinterpret_cast<char*>(xxtea_decrypt(output, outLength, key, keyLength, &retLength));

edited Jun 16 '15 at 07:38

answered Jun 16 '15 at 07:14

Alex Gongalsky

26
2

1

Could you please elaborate more your answer adding a little more description about the solution you provide? – abarisone Jun 16 '15 at 07:23

Base64 encode a XXTEA encrypted string error

2 Answers2