(Objective-C) RSA Encrypt/Decrypt Bytes

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Demonstrates how to RSA encrypt and decrypt byte data.

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#import <CkoPublicKey.h>
#import <CkoRsa.h>
#import <CkoPrng.h>
#import <CkoPrivateKey.h>
#import <NSString.h>

// The RSA public key is used for encryption, and the private key for decryption.

// The public key's role is to make encryption accessible to anyone while ensuring that
// only the private key holder can decrypt the messages.
// The public key is designed to be widely distributed so anyone can use it to encrypt messages
// intended for the owner of the private key.

// Load our 2048-bit RSA public key.
CkoPublicKey *pubKey = [[CkoPublicKey alloc] init];
// In all Chilkat methods expecting a path, you pass either absolute or relative paths.
BOOL success = [pubKey LoadFromFile: @"qa_data/rsaKeys/myTestRsaPublic.pem"];
if (success == NO) {
    NSLog(@"%@",pubKey.LastErrorText);
    return;
}

CkoRsa *rsa = [[CkoRsa alloc] init];

// Tell RSA to use the public key.
[rsa ImportPublicKeyObj: pubKey];

// RSA encryption is for small amounts of data, on the order of 200 bytes or less.
// The maximum number of bytes that can be RSA encrypted depends
// on the RSA key size and padding scheme (OAEP padding vs PKCS#1 v1.5 padding).
// For specific limits, see: RSA Encryption Maximum Number of Bytes

// A typical use for RSA is to encrypt symmetric encryption keys, such as an AES key.
CkoPrng *prng = [[CkoPrng alloc] init];
NSData keyBytes;
keyBytes = [prng GenRandomBytes: [NSNumber numberWithInt: 32]];

NSData encBytes;
encBytes = [rsa EncryptBytes: keyBytes bUsePrivateKey: NO];

// ------------------------------------------------------------------------------------------------------------------------
// Let's decrypt, which requires the matching private key...

// Load the matching 2048-bit RSA private key.
CkoPrivateKey *privKey = [[CkoPrivateKey alloc] init];
NSString *password = @"secret";
success = [privKey LoadAnyFormatFile: @"qa_data/rsaKeys/myTestRsaPrivate.pem" password: password];
if (success == NO) {
    NSLog(@"%@",privKey.LastErrorText);
    return;
}

// Tell the RSA object to use the private key.
[rsa ImportPrivateKeyObj: privKey];

NSData decBytes;
decBytes = [rsa DecryptBytes: encBytes bUsePrivateKey: YES];
if (success == NO) {
    NSLog(@"%@",rsa.LastErrorText);
    return;
}

NSLog(@"%@",@"Success.");