问题
Could someone please help decrypt the base64 string generated by iOS code below into its C# equivalent.
I am trying to end up with "Meet me at the secret location at 8pm" within c#.
iOS generated the following encryption: qd+SGaij5KSBScuLs3TpJS/3Dew8fHTudcs/5MG7Q1kqcrZzZycMgTcQuEEEED5f
This iOS code successfully encrypts and decrypts data as required within XCode 6.
Thank you in advance for your help and support.
Darren
#import <CommonCrypto/CommonCryptor.h>
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSString *sData = @"Meet me at the secret location at 8pm";
NSString *sIv = @"4QesEr03HwE5H1C+ICw7SA==";
NSString *sKey = @"ovA6siPkyM5Lb9oNcnxLz676K6JK6FrJKk4efEUWBzg=";
NSData *dData = [sData dataUsingEncoding:NSUTF8StringEncoding];
NSData *dIv = [sIv dataUsingEncoding:NSUTF8StringEncoding];
NSData *dKey = [sKey dataUsingEncoding:NSUTF8StringEncoding];
NSData *dEncrypt = [self doCipher:dData iv:dIv key:dKey context:kCCEncrypt];
NSData *dDecrypt = [self doCipher:dEncrypt iv:dIv key:dKey context:kCCDecrypt];
NSString *sDecrypt = [[NSString alloc] initWithData:dDecrypt encoding:NSUTF8StringEncoding];
NSLog(@"Decrypted Data: %@",sDecrypt);
}
- (NSData *)doCipher:(NSData *)dataIn
iv:(NSData *)iv
key:(NSData *)symmetricKey
context:(CCOperation)encryptOrDecrypt
{
CCCryptorStatus ccStatus = kCCSuccess;
size_t cryptBytes = 0; // Number of bytes moved to buffer.
NSMutableData *dataOut = [NSMutableData dataWithLength:dataIn.length + kCCBlockSizeAES128];
ccStatus = CCCrypt( encryptOrDecrypt,
kCCAlgorithmAES128,
kCCOptionPKCS7Padding,
symmetricKey.bytes,
kCCKeySizeAES128,
iv.bytes,
dataIn.bytes,
dataIn.length,
dataOut.mutableBytes,
dataOut.length,
&cryptBytes);
if (ccStatus != kCCSuccess) {
NSLog(@"CCCrypt status: %d", ccStatus);
}
dataOut.length = cryptBytes;
NSString *base64 = [dataOut base64EncodedStringWithOptions:0];
NSLog(@"%@",base64);
return dataOut;
}
回答1:
The given base64 string qd+SGaij5KSBScuLs3TpJS/3Dew8fHTudcs/5MG7Q1kqcrZzZycMgTcQuEEEED5f is a two way pack.
First it has to be base64 decoded (which is easy in C#) and afterwards it has to be decrypted by using the correct algorithm. From the given parameters it hopefully uses the AES or Rijndael algorithm (example code here) where you have to put in the base64 decoded bytes, the key and the IV.
After that you hopefully get out your desired data.
So i wrote an example on myself and i'm able to encrypt and decrypt the specified message with C#.
But the retrieved encrypted message differs from the iOS generated message:
Your iOS message: qd+SGaij5KSBScuLs3TpJS/3Dew8fHTudcs/5MG7Q1kqcrZzZycMgTcQuEEEED5f
My C# message: wC2dn+QVhOhf+NqZVskopLdh2XDAdG3SmczrKF+TjQsGfxu07BEhRdiDqkbGY80O
I just made some little changes and dit a little deeper look. One thing i see is that you say in your iOS code that the key has a length of 256 bit. But the key you are providing has only a length of 128 bit. It seems that C# in that case simply switches back to 128 bit key length (cause changing the key size in the code below doesn't change the encrypted bytes). But maybe the CCCrypt in iOS makes something different. So either adopt in your iOS code the key size or provider a 256 bit key and than compare the results of iOS and C# again.
Example:
var message = @"Meet me at the secret location at 8pm";
var iv = @"4QesEr03HwE5H1C+ICw7SA==";
var key = @"ovA6siPkyM5Lb9oNcnxLz676K6JK6FrJKk4efEUWBzg=";
byte[] encryptedBytes;
using (var aesCryptoProvider = new AesCryptoServiceProvider())
{
aesCryptoProvider.BlockSize = 128;
aesCryptoProvider.KeySize = 256;
aesCryptoProvider.IV = Convert.FromBase64String(iv);
aesCryptoProvider.Key = Convert.FromBase64String(key);
aesCryptoProvider.Padding = PaddingMode.PKCS7;
aesCryptoProvider.Mode = CipherMode.CBC;
using (var encryptor = aesCryptoProvider.CreateEncryptor())
using (var memoryStream = new MemoryStream())
using (var cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
using (var streamWriter = new StreamWriter(cryptoStream, Encoding.UTF8))
{
streamWriter.Write(message);
streamWriter.Close();
encryptedBytes = memoryStream.ToArray();
}
}
var encryptedMessage = Convert.ToBase64String(encryptedBytes);
Console.WriteLine(encryptedMessage);
using (var aesCryptoProvider = new AesCryptoServiceProvider())
{
aesCryptoProvider.BlockSize = 128;
aesCryptoProvider.KeySize = 256;
aesCryptoProvider.IV = Convert.FromBase64String(iv);
aesCryptoProvider.Key = Convert.FromBase64String(key);
aesCryptoProvider.Padding = PaddingMode.PKCS7;
aesCryptoProvider.Mode = CipherMode.CBC;
using (var decryptor = aesCryptoProvider.CreateDecryptor())
using (var memoryStream = new MemoryStream(Convert.FromBase64String(encryptedMessage)))
using (var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
using (var streamReader = new StreamReader(cryptoStream, Encoding.UTF8))
{
Console.WriteLine(streamReader.ReadToEnd());
}
}
回答2:
The encrypted text on each platform now reads:
X/aopyVDDva/wJ3If/5i73JGjwth9eH45Opxaaswgb8Kx3ynh8BhBTFRrHT0/i3y
Here is the working C# code
NOTE: C# code extracted from https://github.com/Pakhee/Cross-platform-AES-encryption
namespace CryptoTest
{
public partial class Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
string iv = "4QesEr03HwE5H1C+ICw7SA=="; // origional iv 128 bits
string key = "ovA6siPkyM5Lb9oNcnxLz676K6JK6FrJKk4efEUWBzg="; // origional key 256 bits
string message = "Meet me at the secret location at 8pm";
CryptLib cryptLib = new CryptLib();
string encryptedText = cryptLib.encrypt(message, key, iv);
string originalMessage = cryptLib.decrypt(encryptedText, key, iv);
Debug.WriteLine(originalMessage);
}
}
public class CryptLib
{
UTF8Encoding _enc;
RijndaelManaged _rcipher;
byte[] _key, _pwd, _ivBytes, _iv;
private enum EncryptMode { ENCRYPT, DECRYPT };
public CryptLib()
{
_enc = new UTF8Encoding();
_rcipher = new RijndaelManaged();
_rcipher.Mode = CipherMode.CBC;
_rcipher.Padding = PaddingMode.PKCS7;
_rcipher.KeySize = 256;
_rcipher.BlockSize = 128;
_key = new byte[32];
_iv = new byte[_rcipher.BlockSize / 8]; //128 bit / 8 = 16 bytes
_ivBytes = new byte[16];
}
private String encryptDecrypt(string _inputText, string _encryptionKey, EncryptMode _mode, string _initVector)
{
string _out = "";// output string
_pwd = Encoding.UTF8.GetBytes(_encryptionKey);
_ivBytes = Encoding.UTF8.GetBytes(_initVector);
int len = _pwd.Length;
if (len > _key.Length)
{
len = _key.Length;
}
int ivLenth = _ivBytes.Length;
if (ivLenth > _iv.Length)
{
ivLenth = _iv.Length;
}
Array.Copy(_pwd, _key, len);
Array.Copy(_ivBytes, _iv, ivLenth);
_rcipher.Key = _key;
_rcipher.IV = _iv;
if (_mode.Equals(EncryptMode.ENCRYPT))
{
//encrypt
byte[] plainText = _rcipher.CreateEncryptor().TransformFinalBlock(_enc.GetBytes(_inputText), 0, _inputText.Length);
_out = Convert.ToBase64String(plainText);
}
if (_mode.Equals(EncryptMode.DECRYPT))
{
//decrypt
byte[] plainText = _rcipher.CreateDecryptor().TransformFinalBlock(Convert.FromBase64String(_inputText), 0, Convert.FromBase64String(_inputText).Length);
_out = _enc.GetString(plainText);
}
_rcipher.Dispose();
return _out;// return encrypted/decrypted string
}
public string encrypt(string _plainText, string _key, string _initVector)
{
return encryptDecrypt(_plainText, _key, EncryptMode.ENCRYPT, _initVector);
}
public string decrypt(string _encryptedText, string _key, string _initVector)
{
return encryptDecrypt(_encryptedText, _key, EncryptMode.DECRYPT, _initVector);
}
}
}
Here is the working iOS code
#import <CommonCrypto/CommonCryptor.h>
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSString *sData = @"Meet me at the secret location at 8pm";
NSString *sIv = @"4QesEr03HwE5H1C+ICw7SA==";
NSString *sKey = @"ovA6siPkyM5Lb9oNcnxLz676K6JK6FrJKk4efEUWBzg=";
NSData *dData = [sData dataUsingEncoding:NSUTF8StringEncoding];
NSData *dEncrypt = [self doCipher:dData key:sKey iv:sIv context:kCCEncrypt];
NSData *base64 = [dEncrypt base64EncodedDataWithOptions:0];
NSString *sBase64 = [[NSString alloc] initWithData:base64 encoding:NSUTF8StringEncoding];
NSLog(@"Base64 String: %@",sBase64);
NSData *dDecrypt= [self decrypt:dEncrypt key:sKey iv:sIv];
NSString *sDecrypt = [[NSString alloc] initWithData:dDecrypt encoding:NSUTF8StringEncoding];
NSLog(@"Decrypted Data: %@",sDecrypt);
}
- (NSData *)doCipher:(NSData *)plainText
key:(NSString *)key
iv:(NSString *)iv
context:(CCOperation)encryptOrDecrypt
{
NSUInteger dataLength = [plainText length];
size_t buffSize = dataLength + kCCBlockSizeAES128;
void *buff = malloc(buffSize);
size_t numBytesEncrypted = 0;
NSData *dIv = [iv dataUsingEncoding:NSUTF8StringEncoding];
NSData *dKey = [key dataUsingEncoding:NSUTF8StringEncoding];
CCCryptorStatus status = CCCrypt(encryptOrDecrypt,
kCCAlgorithmAES128,
kCCOptionPKCS7Padding,
dKey.bytes, kCCKeySizeAES256,
dIv.bytes,
[plainText bytes], [plainText length],
buff, buffSize,
&numBytesEncrypted);
if (status == kCCSuccess) {
return [NSData dataWithBytesNoCopy:buff length:numBytesEncrypted];
}
free(buff);
return nil;
}
来源：https://stackoverflow.com/questions/26242317/decrypt-a-base64-string-using-c-sharp-generated-by-ios-cccrypt-function-using-ae