decrypt using RSA private key error OSStatus -50

Hi

I am trying to decrypt using RSA private key but i get OSStatus -50 error.

Any help is appriciated.

here is my code :

const size_t BUFFER_SIZE = 128;

const size_t CIPHER_BUFFER_SIZE = 1024;

const uint32_t PADDING = kSecPaddingPKCS1;

- (NSString *)privateKeyDecryptionOnString: (NSString*)message {

uint8_t *cipherBuffer;

uint8_t *decryptedBuffer;

const char* utf8String = [message cStringUsingEncoding:NSUTF8StringEncoding];

cipherBuffer = (uint8_t *)calloc(1024, sizeof(uint8_t));

decryptedBuffer = (uint8_t *)calloc(BUFFER_SIZE, sizeof(uint8_t));

cipherBuffer = (uint8_t *)utf8String;

NSLog(@"encrypted data: %s", cipherBuffer);

[self decryptWithPrivateKey:cipherBuffer plainBuffer:decryptedBuffer];

NSLog(@"decrypted data: %s", decryptedBuffer);

NSString *string = [NSString stringWithUTF8String:(char *)decryptedBuffer];

free(cipherBuffer);

free(decryptedBuffer);

return string;

}

- (void)decryptWithPrivateKey:(uint8_t *)cipherBuffer plainBuffer:(uint8_t *)plainBuffer

{

OSStatus status = noErr;

size_t cipherBufferSize = strlen((char *)cipherBuffer);

NSLog(@"decryptWithPrivateKey: length of buffer: %lu", BUFFER_SIZE);

NSLog(@"decryptWithPrivateKey: length of input: %lu", cipherBufferSize);

// DECRYPTION

size_t plainBufferSize = BUFFER_SIZE;

// Error handling

NSLog(@"%zu",SecKeyGetBlockSize([self getPrivateKeyRef]));

status = SecKeyDecrypt([self getPrivateKeyRef],

PADDING,

&cipherBuffer[0],

cipherBufferSize,

&plainBuffer[0],

&plainBufferSize

);

NSLog(@"decryption result code: %ld (size: %lu)", status, plainBufferSize);

NSLog(@"FINAL decrypted text: %s", plainBuffer);

}