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I encrypt a login in php with this script :

//PHP Code
    function cypherAES128($plaintext, $key)
{
    $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_ECB);
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);


    $ciphertext = mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $plaintext, MCRYPT_MODE_ECB/*, $iv*/);
    $ciphertext = base64_encode($ciphertext);

    return $ciphertext;
}

function uncypherAES128($ciphertext, $key)
{
    $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_ECB);
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);  

    $ciphertext = base64_decode($ciphertext);
    $plaintext = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, $ciphertext, MCRYPT_MODE_ECB/*, $iv*/);      
    return $plaintext;
}

I get the encrypted password in my iOS app, and try to decrypt it with FBEncryptorAES.

I can get the login decrypted back if it is smaller than 16 character.

//PHP Code
echo cypherAES128("aShortLogin", $key);   //this encrypted login can be decrypted
echo cypherAES128("loginGreaterThan16Characters", $key);   //this encrypted login cannot

When the encrypted word is greater than 15 char, I got a kCCDecodeError -4304.

A little precision : It sounds like long login can be encrypted then decrypted whithin the PHP script, AND encrypted then decrypted with FBEncryptor. Only PHP encrypt => objectiveC decrypt doesn't works

Any idea please?? I'm a beginner in iOS and cryptography.

Thanks in advance, and sorry for my poor english.

[EDIT] Don't sure the problem is only the objectiveC, because as I said, the FBEncryptor can decode text it encoded itself.

The error appears when I excecute this code : 

//Objective-C code:
NSString * decryptedLogin = [FBEncryptorAES decryptBase64String: encryptedLogin keyString:AESKey];

Whith "encryptedLogin" = the value returned by the PHP script. Changing value and lenght of AESKey doesn't seem to work. (AESKey = same key as the $key in PHP) Tried 16 & 32 bytes length key.

I don't changed the code in FBEncryptorAES, here is decryptBase64String : 

//Objective-C code
+ (NSData*)decryptData:(NSData*)data key:(NSData*)key iv:(NSData*)iv;
{
NSData* result = nil;

// setup key
unsigned char cKey[FBENCRYPT_KEY_SIZE];
bzero(cKey, sizeof(cKey));
[key getBytes:cKey length:FBENCRYPT_KEY_SIZE];

// setup iv
char cIv[FBENCRYPT_BLOCK_SIZE];
bzero(cIv, FBENCRYPT_BLOCK_SIZE);
if (iv) {
    [iv getBytes:cIv length:FBENCRYPT_BLOCK_SIZE];
}

// setup output buffer
size_t bufferSize = [data length] + FBENCRYPT_BLOCK_SIZE;
void *buffer = malloc(bufferSize);

// do decrypt
size_t decryptedSize = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
                                      FBENCRYPT_ALGORITHM,
                                      kCCOptionPKCS7Padding,
                                      cKey,
                                      FBENCRYPT_KEY_SIZE,
                                      cIv,
                                      [data bytes],
                                      [data length],
                                      buffer,
                                      bufferSize,
                                      &decryptedSize);

if (cryptStatus == kCCSuccess) {
    result = [NSData dataWithBytesNoCopy:buffer length:decryptedSize];
} else {
    free(buffer);
    NSLog(@"[ERROR] failed to decrypt| CCCryptoStatus: %d", cryptStatus);
}

return result;
}

The String is converted into a Base64 string. I don't think that the conversion is the problem.

4

1 に答える 1

1

問題が解決しました！！！！

私のphpスクリプトでは、「MCRYPT_MODE_ECB」の代わりに「MCRYPT_MODE_CBC」を使用してください。

//PHP Code: 
  // $key must be 32 bytes
  $key="32-AAAAAAAAAAAAAAAAAAAAAAAAAAAAA";


    function cypherAES128($plaintext, $key)
{
    $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);


    $ciphertext = mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $plaintext, MCRYPT_MODE_CBC/*, $iv*/);
    $ciphertext = base64_encode($ciphertext);

    return $ciphertext;
}

function uncypherAES128($ciphertext, $key)
{
    $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);  

    $ciphertext = base64_decode($ciphertext);
    $plaintext = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, $ciphertext, MCRYPT_MODE_CBC/*, $iv*/);      
    return $plaintext;
}

AES で暗号化するには 5 つの方法があり、私の iOS コード / PHP コードは同じ方法を使用していないようです。

ご回答ありがとうございます。これがお役に立てば幸いです。

于 2012-05-17T13:17:47.150 に答える