iPhone RSA text encoding + decoding - iphone

Question

What should happen.
User send encrypted message to the server. Other user retrieve message from the the server and then decript it. And vice versa.
I have some text in unicode encoding. Text should send to the server using RSA encription as a part of JSON (like {"message" : ""} )
To encript text I create function that have NSString as an input parametr and NSString as an output parametr. Decript function have the same format.
My problem: text that is a result of decode function not the same that was encoded.
-(NSString*) encryptText:(NSString*) text {
OSStatus status = noErr;
//text = #"ネイティブ英会話";
text = #"test text";
int length = [text lengthOfBytesUsingEncoding:NSUTF8StringEncoding];
const char *cText = [text cStringUsingEncoding:NSUTF8StringEncoding];
size_t cipherBufferSize = BUFFER_SIZE;
if (cipherBufferSize < length) {
cipherBufferSize = length;
}
char *cipherBuffer = malloc(cipherBufferSize);
memset(cipherBuffer, 0, cipherBufferSize);
NSLog(#"BEFORE SIPHER TEXT = %s", cText);
status = SecKeyEncrypt(_publicKey,
kSecPaddingNone,
(unsigned char*) cText,
length,
(unsigned char*) cipherBuffer,
&cipherBufferSize
);
NSLog(#"CIPHER TEXT = %s", cipherBuffer);
NSString *result = nil;
if (status == 0) {
result = [NSString stringWithFormat:#"%s", cipherBuffer];
}
free(cipherBuffer);
return result;
}
-(NSString*) decriptText:(NSString*) encriptedText {
OSStatus status = noErr;
const char *cText = [encriptedText cStringUsingEncoding:NSUTF8StringEncoding];
int length = [encriptedText lengthOfBytesUsingEncoding:NSUTF8StringEncoding];
size_t plainBufferSize = BUFFER_SIZE;
if (plainBufferSize < length) {
plainBufferSize = length;
}
char *plainBuffer = malloc(plainBufferSize);
memset(plainBuffer, 0, plainBufferSize);
NSLog(#"BEFORE DECIPHER TEXT = %s", cText);
status = SecKeyDecrypt(_privateKey,
kSecPaddingNone,
(unsigned char *) cText,
length,
(unsigned char *) plainBuffer,
&plainBufferSize
);
NSLog(#"AFTER DESIPHER BUFFER = %s status = %d", plainBuffer, status);
NSString *decriptedText = nil;
if (status == 0) {
decriptedText = [NSString stringWithUTF8String:plainBuffer];
}
free(plainBuffer);
return decriptedText;
}