Objective-C

Demonstrate RSA Encrypt/Decrypt using BinData

See more RSA Examples

Demonstrates how to RSA encrypt and decrypt data contained in a Chilkat BinData object. Objective-C

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

BOOL success = NO;

//  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.
success = [pubKey LoadFromFile: @"rsaKeys/myTestRsaPublic.pem"];
if (success == NO) {
    NSLog(@"%@",pubKey.LastErrorText);
    return;
}

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

//  Tell RSA to use the public key.
[rsa UsePublicKey: 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

//  Create some binary data to encrypt.
CkoBinData *bd = [[CkoBinData alloc] init];
int i = 0;
for (i = 0; i <= 49; i++) {
    [bd AppendByte: [NSNumber numberWithInt: i]];
}

//  Show the bytes to be encrypted in hex format:
NSLog(@"%@%@",@"To be encrypted: ",[bd GetEncoded: @"hex"]);

//  To be encrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031

//  RSA encrypt the contents of the bd, replacing the contents with the RSA encrypted data.
[rsa EncryptBd: bd usePrivateKey: NO];

//  Now it is encrypted.
NSLog(@"%@%d",@"Encrypted size = ",[bd.NumBytes intValue]);
NSLog(@"%@",[bd GetEncoded: @"hex"]);

//  Encrypted size = 256
//  749ED9D0A8767C06C09AD9697F654F86B145F966722F9714902C4175BDBD02E68984ECF111D4D461
//  EDB4A8E677D399D19CCA60F35C6DE9972F4262880FE9D77DB75915393E8E7DB80AAB5E383013FAEB
//  60C77D1E6FECC9A7C8426976416C6218FE7DA998EE063CE709E79C240F8625F4A56A0A33AFD63F7A
//  BA26F2A692B42E878C53B78602C725FE63FF961A46A2B9D436E5E3D9D64AE3F1D1F5AD5F5B47FCD69
//  447306B77F2FD6D766CCAA1A110A3371586B43DF0D7FFE2220D1B305CF9371AC342F849FB0C90CD99E
//  C176928D877FE1C0DE1A7CB6EB824FEC7E1DCF90EF2C6BA9F1DFD3EBFBE89C51AF074DC6AE02E544A78
//  5018C36D3D48B2EF5202AF61AC

//  ------------------------------------------------------------------------------------------------------------------------
//  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: @"rsaKeys/myTestRsaPrivate.pem" password: password];
if (success == NO) {
    NSLog(@"%@",privKey.LastErrorText);
    return;
}

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

//  Decrypt
success = [rsa DecryptBd: bd usePrivateKey: YES];
if (success == NO) {
    NSLog(@"%@",rsa.LastErrorText);
    return;
}

//  Examine the contents of bd to see if it now contains the unencrypted original data.
NSLog(@"%@%@",@"Decrypted: ",[bd GetEncoded: @"hex"]);

//  Decrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031