objective-c Chinese encrypts and decrypts garbled

/ / Encryption
NSData * plain = [texUid.text dataUsingEncoding: NSUTF8StringEncoding];
NSData * eData = [plain AES256EncryptWithKey: key];
NSString * secretString = [eData base64EncodedString];
NSLog (@ "encrypted string:% @", secretString);


/ / Decryption
NSString * enString = [NSString stringWithString: secretString];
NSData * cipher = [NSData dataFromBase64String: enString];
NSData * bDecrypt = [cipher AES256DecryptWithKey: key];
NSString * dateString = [[NSString alloc] initWithData: bDecrypt encoding: NSASCIIStringEncoding];



NSLog (@ "decrypted string:% @", dateString); / / solution out of the Chinese is garbled, expert advice thank you
Reply:
Encrypted data using the encoding format: NSUTF8StringEncoding
Decrypt data using the encoding format: NSASCIIStringEncoding

Reply:
Ah, to solve, to decrypt the coding format is wrong.