I am trying to use the same key and VI to encrypt and decryp the same message, say aabbcc@gmail.com. The key length is 128 bit as I know that in Java/Android, 256 is not easy to implement.
Here is my function to do the AES encryption using Crypto++
string encryptString(string toBeEncrypted) {
//
// Create Cipher Text
//
CryptoPP::AES::Encryption aesEncryption(key, CryptoPP::AES::DEFAULT_KEYLENGTH);
CryptoPP::CBC_Mode_ExternalCipher::Encryption cbcEncryption(aesEncryption, iv);
std::string ciphertext;
std::cout << "To be encrypted (" << toBeEncrypted.size() << " bytes)" << std::endl;
std::cout << toBeEncrypted;
std::cout << std::endl << std::endl;
CryptoPP::StreamTransformationFilter stfEncryptor(cbcEncryption, new CryptoPP::StringSink(ciphertext), CryptoPP::StreamTransformationFilter::PKCS_PADDING);
stfEncryptor.Put(reinterpret_cast<const unsigned char*> (toBeEncrypted.c_str()), toBeEncrypted.length() + 1);
stfEncryptor.MessageEnd();
}
key is "4ff539a893fed04840749287bb3e4152" and IV is "79f564e83be16711759ac7c730072bd0".
They are stored in binary in a ubuntu running in VMWare on a x86 Windows.
The function to convert key and iv from byte to hex array is:
std::string hexToStr(unsigned char *data, int len)
{
std::stringstream ss;
ss<<std::hex;
for(int i(0);i<len;++i){
ss<<std::setfill('0')<<std::setw(2)<<(int)data[i];
}
return ss.str();
}
I checked the hex string vs the memory of byte array key and iv, and they are matching.
The results for encrypting aabbcc@gmail.com is c08a50b45ff16650542e290e05390a6c6fe533e11e9f802ad7d47681fd41f964 from C++.
I obtained this by passing the returned string ciphertext into the function hexToStr like cout<<TFFHelper::hexStr((unsigned char *)ciphertext.c_str(), ciphertext.length())<<endl;
I can also decrpt it with the following function, and I passed the raw string rather than the hex string into this function.
string TFFEncryption::decryptString(string toBeDecrypted) {
string decryptedtext;
CryptoPP::AES::Decryption aesDecryption(key, CryptoPP::AES::DEFAULT_KEYLENGTH);
CryptoPP::CBC_Mode_ExternalCipher::Decryption cbcDecryption(aesDecryption, iv);
CryptoPP::StreamTransformationFilter stfDecryptor(cbcDecryption, new CryptoPP::StringSink(decryptedtext), CryptoPP::StreamTransformationFilter::PKCS_PADDING);
stfDecryptor.Put(reinterpret_cast<const unsigned char*> (toBeDecrypted.c_str()), toBeDecrypted.size());
stfDecryptor.MessageEnd();
return decryptedtext;
}
I put the same VI and KEY in my Android code, and try to encrypt. It ends up in a half matching results after encrypting.
Android code is as follow:
public class myAES {
private static final String key = "4ff539a893fed04840749287bb3e4152";
private static final String initVector = "79f564e83be16711759ac7c730072bd0";
private final static char[] hexArray = "0123456789ABCDEF".toCharArray();
public static byte[] hexStringToByteArray(String s) {
int len = s.length();
byte[] data = new byte[len / 2];
for (int i = 0; i < len; i += 2) {
data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)
+ Character.digit(s.charAt(i+1), 16));
}
return data;
}
public static String bytesToHex(byte[] bytes) {
char[] hexChars = new char[bytes.length * 2];
for ( int j = 0; j < bytes.length; j++ ) {
int v = bytes[j] & 0xFF;
hexChars[j * 2] = hexArray[v >>> 4];
hexChars[j * 2 + 1] = hexArray[v & 0x0F];
}
return new String(hexChars);
}
public static byte[] encrypt(String value) {
try {
IvParameterSpec iv = new IvParameterSpec(hexStringToByteArray(initVector));
SecretKeySpec skeySpec = new SecretKeySpec(hexStringToByteArray(key), "AES");
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
cipher.init(Cipher.ENCRYPT_MODE, skeySpec, iv);
byte[] encrypted = cipher.doFinal(value.getBytes());
Log.v("Encryption successful", bytesToHex(encrypted));
return encrypted;
} catch (Exception ex) {
ex.printStackTrace();
}
return null;
}
public static String decrypt(byte[] encrypted) {
try {
IvParameterSpec iv = new IvParameterSpec(hexStringToByteArray(initVector));
SecretKeySpec skeySpec = new SecretKeySpec(hexStringToByteArray(key), "AES");
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
cipher.init(Cipher.DECRYPT_MODE, skeySpec, iv);
byte[] original = cipher.doFinal(encrypted);
Log.v("Decryption successful", new String(original, "UTF-8"));
return new String(original);
} catch (Exception ex) {
ex.printStackTrace();
}
return null;
}
}
I got the result of C08A50B45FF16650542E290E05390A6CFE5466FC480F0667517B248410930B69.
I used the same piece of code in Netbeans on Java8, running on the same Ubuntu of the C++ code, and got exactly the same results as what I mentioned on the previous line (Android results). I don't think this is OS dependent, but probably I did something wrong with either Java or C++ in my code.
So the first half of the hex strings are matching, and the later half is not. I tried to reduced the phrase aabbcc@gmail.com into abc@gmail.com, which results in complete different results from C++ vs Java (Ubuntu vs Android).
However, if I decrpt that binary array in Java, I got the original phrase aabbcc@gmail.com or abc@gmail.com.
I have the following questions.
- What did I do wrong?
- Is it the proper way to case
const char *intounsigned char *? I think it should be OK as I am getting the hex string of the binary - Is the half matching results caused by padding?
