CODEWITHSUNDEEP
iosiphoneobjective-cencryptiondes
Sudha Tiwari
Sudha Tiwari

Reputation: 2461

DES decryption issue

I am using DES decryption with ECB mode. I am using the following code for decryption :

NSString *token = @"kRAz86UoZd5tFKf0xv8TKg==";
NSString *key = @"meristem";

const void *vplainText;
size_t plainTextBufferSize;

NSData *EncryptData = [[NSData alloc] initWithBase64EncodedString:token options:0];
plainTextBufferSize = [EncryptData length];
vplainText = [EncryptData bytes];

//plainTextBufferSize = [token length];
//vplainText = (const void *) [token UTF8String];

CCCryptorStatus ccStatus;
uint8_t *bufferPtr = NULL;
size_t bufferPtrSize = 0;
size_t movedBytes;

bufferPtrSize = (plainTextBufferSize + kCCBlockSize3DES) & ~(kCCBlockSize3DES - 1);
bufferPtr = malloc( bufferPtrSize * sizeof(uint8_t));
memset((void *)bufferPtr, 0x0, bufferPtrSize);

NSString *initVec = @"init Vec";
const void *vkey = (const void *) [key UTF8String];
const void *vinitVec;
vinitVec = (const void *) [initVec UTF8String];

ccStatus = CCCrypt(kCCDecrypt,
                   kCCAlgorithmDES,
                   kCCOptionPKCS7Padding | kCCOptionECBMode,
                   vkey, //"123456789012345678901234", //key
                   kCCKeySizeDES,
                   NULL,// vinitVec, //"init Vec", //iv,
                   vplainText, //"Your Name", //plainText,
                   plainTextBufferSize,
                   (void *)bufferPtr,
                   bufferPtrSize,
                   &movedBytes);

NSData *myData = [NSData dataWithBytes:(const void *)bufferPtr length:(NSUInteger)movedBytes];
NSString *decodedString = [[NSString alloc] initWithData:myData encoding:NSUTF8StringEncoding];
NSLog(@"dis is data %@",decodedString);

Here, you can see that my encrypted string is kRAz86UoZd5tFKf0xv8TKg== and its result is vishal thakur. But by using the above code for decryption, I am getting only vishal t. I cant understand why am not getting the full string. Please can anyone tell me what I am doing wrong.

Upvotes: 4

Views: 681

Answers (2)

0xKayvan
0xKayvan

Reputation: 376

Edited: I think it has something to do with plainTextBufferSize, and this cause the problem as you call it in your CCCrypt function.

Try changing its value before CCCrypt function.

Upvotes: 1

Sudha Tiwari
Sudha Tiwari

Reputation: 2461

I have solved my issue by replacing this line 

plainTextBufferSize = [EncryptData length];

into 

plainTextBufferSize = [EncryptData length]+1;

Upvotes: 2

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