I am trying to decrypt data from a .NET server in an iOS application. The data has been encrypted with 3DES in ECB mode. I was able to successfully decrypt this same data on Android, but on IOS I just keep getting garbage output.
I've compared the encrypted bytes and digested key bytes between iOS and Android and they appear to be the same (although I had to convert the signed Java bytes into a hex representation to be able to compare to xcode debugger). However, the Java crypto objects` are higher level than Common Crypto, so I'm not confident that I've prepared the key correctly. Please take a look at the following code - any feedback is welcome.
//read the encrypted data from file into NSData
NSString *servicesPath = [NSString stringWithString:[[AppMobiDelegate applicationDocumentsDirectory] stringByAppendingPathComponent:@"services.xml"]];
NSData *servicesData = [NSData dataWithContentsOfFile:servicesPath];
//setup crypto objects
const void *vEncryptedText = [servicesData bytes];
size_t encryptedTextBufferSize = [servicesData length];
CCCryptorStatus ccStatus;
uint8_t *bufferPtr = NULL;
size_t bufferPtrSize = 0;
size_t movedBytes = 0;
bufferPtrSize = (encryptedTextBufferSize + kCCBlockSize3DES) & ~(kCCBlockSize3DES - 1);
bufferPtr = malloc( bufferPtrSize * sizeof(uint8_t));
memset((void *)bufferPtr, 0x0, bufferPtrSize);
//get a cstring with key data
const char *cStr = [@"FAKEKEY" cStringUsingEncoding:UTF8String];
//make a 16 byte array to put the md5 digested data into
unsigned char md5[CC_MD5_DIGEST_LENGTH];
bzero( md5, sizeof(md5) );
CC_MD5( cStr, strlen(cStr), md5 );
//make a 24 byte array so we have correct size for 3des key and copy digest data in
unsigned char key[kCCKeySize3DES];
bzero( key, sizeof(key) );
memcpy(key, md5, sizeof(md5));
//decrypt data and return string
ccStatus = CCCrypt(kCCDecrypt,
kCCAlgorithm3DES,
kCCOptionECBMode, //kCCOptionPKCS7Padding kCCOptionECBMode
key, //vKey md5
kCCKeySize3DES,
NULL,
vEncryptedText,
encryptedTextBufferSize,
(void *)bufferPtr,
bufferPtrSize,
&movedBytes);
if (ccStatus == kCCParamError) return @"PARAM ERROR";
else if (ccStatus == kCCBufferTooSmall) return @"BUFFER TOO SMALL";
else if (ccStatus == kCCMemoryFailure) return @"MEMORY FAILURE";
else if (ccStatus == kCCAlignmentError) return @"ALIGNMENT";
else if (ccStatus == kCCDecodeError) return @"DECODE ERROR";
else if (ccStatus == kCCUnimplemented) return @"UNIMPLEMENTED";
NSString *result = [[[NSString alloc] initWithData: [NSData dataWithBytes:(const void *)bufferPtr length:(NSUInteger)movedBytes] encoding:NSASCIIStringEncoding] autorelease];
return result;
