CryptoExcercise Encryption/Decryption Problem - iphone

Question

I am using apples "cryptoexcercise" (Security.Framework) in my application to encrypt and decrypt a data of numeric value. When I give the input 950,128 the values got encrypted, but it is not getting decrypted and exists with the encrypted value only. This happens only with the mentioned numeric values. Could you please check this issue and give the solution to solve this problem?
here is my code
(void)testAsymmetricEncryptionAndDecryption {
uint8_t *plainBuffer; uint8_t *cipherBuffer; uint8_t *decryptedBuffer;
const char inputString[] = "950"; int len = strlen(inputString);
if (len > BUFFER_SIZE) len = BUFFER_SIZE-1;
plainBuffer = (uint8_t *)calloc(BUFFER_SIZE, sizeof(uint8_t)); cipherBuffer = (uint8_t *)calloc(CIPHER_BUFFER_SIZE, sizeof(uint8_t)); decryptedBuffer = (uint8_t *)calloc(BUFFER_SIZE, sizeof(uint8_t));
strncpy( (char *)plainBuffer, inputString, len);
NSLog(#"plain text : %s", plainBuffer);
[self encryptWithPublicKey:(UInt8 *)plainBuffer cipherBuffer:cipherBuffer];
NSLog(#"encrypted data: %s", cipherBuffer);
[self decryptWithPrivateKey:cipherBuffer plainBuffer:decryptedBuffer];
NSLog(#"decrypted data: %s", decryptedBuffer);
free(plainBuffer); free(cipherBuffer); free(decryptedBuffer); }
(void)encryptWithPublicKey:(uint8_t *)plainBuffer cipherBuffer:(uint8_t *)cipherBuffer {
OSStatus status = noErr;
size_t plainBufferSize = strlen((char *)plainBuffer); size_t cipherBufferSize = CIPHER_BUFFER_SIZE;
NSLog(#"SecKeyGetBlockSize() public = %d", SecKeyGetBlockSize([self getPublicKeyRef])); // Error handling // Encrypt using the public. status = SecKeyEncrypt([self getPublicKeyRef], PADDING, plainBuffer, plainBufferSize, &cipherBuffer[0], &cipherBufferSize ); NSLog(#"encryption result code: %d (size: %d)", status, cipherBufferSize); NSLog(#"encrypted text: %s", cipherBuffer); }
(void)decryptWithPrivateKey:(uint8_t *)cipherBuffer plainBuffer:(uint8_t *)plainBuffer { OSStatus status = noErr;
size_t cipherBufferSize = strlen((char *)cipherBuffer);
NSLog(#"decryptWithPrivateKey: length of buffer: %d", BUFFER_SIZE); NSLog(#"decryptWithPrivateKey: length of input: %d", cipherBufferSize);
// DECRYPTION size_t plainBufferSize = BUFFER_SIZE;
// Error handling status = SecKeyDecrypt([self getPrivateKeyRef], PADDING, &cipherBuffer[0], cipherBufferSize, &plainBuffer[0], &plainBufferSize ); NSLog(#"decryption result code: %d (size: %d)", status, plainBufferSize); NSLog(#"FINAL decrypted text: %s", plainBuffer);
}
(SecKeyRef)getPublicKeyRef { OSStatus sanityCheck = noErr; SecKeyRef publicKeyReference = NULL;
if (publicKeyRef == NULL) { NSMutableDictionary *queryPublicKey = [[NSMutableDictionary alloc] init];
// Set the public key query dictionary.
[queryPublicKey setObject:(id)kSecClassKey forKey:(id)kSecClass];
[queryPublicKey setObject:publicTag forKey:(id)kSecAttrApplicationTag];
[queryPublicKey setObject:(id)kSecAttrKeyTypeRSA forKey:(id)kSecAttrKeyType];
[queryPublicKey setObject:[NSNumber numberWithBool:YES] forKey:(id)kSecReturnRef];
// Get the key.
sanityCheck = SecItemCopyMatching((CFDictionaryRef)queryPublicKey, (CFTypeRef *)&publicKeyReference);
if (sanityCheck != noErr)
{
publicKeyReference = NULL;
}
[queryPublicKey release];
} else { publicKeyReference = publicKeyRef; }
return publicKeyReference; }
(SecKeyRef)getPrivateKeyRef { OSStatus resultCode = noErr; SecKeyRef privateKeyReference = NULL;
if(privateKeyRef == NULL) { NSMutableDictionary * queryPrivateKey = [[NSMutableDictionary alloc] init];
// Set the private key query dictionary.
[queryPrivateKey setObject:(id)kSecClassKey forKey:(id)kSecClass];
[queryPrivateKey setObject:privateTag forKey:(id)kSecAttrApplicationTag];
[queryPrivateKey setObject:(id)kSecAttrKeyTypeRSA forKey:(id)kSecAttrKeyType];
[queryPrivateKey setObject:[NSNumber numberWithBool:YES] forKey:(id)kSecReturnRef];
// Get the key.
resultCode = SecItemCopyMatching((CFDictionaryRef)queryPrivateKey, (CFTypeRef *)&privateKeyReference);
NSLog(#"getPrivateKey: result code: %d", resultCode);
if(resultCode != noErr)
{
privateKeyReference = NULL;
}
[queryPrivateKey release];
} else { privateKeyReference = privateKeyRef; }
return privateKeyReference; }

Answer 1

I am sorry for the late reply... but your example worked perfectly for me, except the fact,
1) for privateTag and publicTag I had to declare
NSData *privateTag = [NSData dataWithBytes:privateKeyIdentifier length:strlen((const char *)privateKeyIdentifier)];
NSData *publicTag = [NSData dataWithBytes:publicKeyIdentifier length:strlen((const char *)privateKeyIdentifier)];
2) and also changing privateKey == NULL rather than privateKeyRef ==NULL in the key reference IF condition..