(Objective-C) RSA Encrypt and Decrypt Strings

Objective-C sample code to RSA public-key encrypt and decrypt strings using public and private keys.

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#import <CkoRsa.h>
#import <NSString.h>

// This example assumes the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

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

// This example also generates the public and private
// keys to be used in the RSA encryption.
// Normally, you would generate a key pair once,
// and distribute the public key to your partner.
// Anything encrypted with the public key can be
// decrypted with the private key.  The reverse is 
// also true: anything encrypted using the private
// key can be decrypted using the public key.

// Generate a 1024-bit key.  Chilkat RSA supports
// key sizes ranging from 512 bits to 4096 bits.
BOOL success = [rsa GenerateKey: [NSNumber numberWithInt: 1024]];
if (success != YES) {
    NSLog(@"%@",rsa.LastErrorText);
    return;
}

// Keys are exported in XML format:
NSString *publicKey = [rsa ExportPublicKey];
NSString *privateKey = [rsa ExportPrivateKey];

NSString *plainText = @"Encrypting and decrypting should be easy!";

// Start with a new RSA object to demonstrate that all we
// need are the keys previously exported:
CkoRsa *rsaEncryptor = [[CkoRsa alloc] init];

// Encrypted output is always binary.  In this case, we want
// to encode the encrypted bytes in a printable string.
// Our choices are "hex", "base64", "url", "quoted-printable".
rsaEncryptor.EncodingMode = @"hex";

// We'll encrypt with the public key and decrypt with the private
// key.  It's also possible to do the reverse.
success = [rsaEncryptor ImportPublicKey: publicKey];

BOOL usePrivateKey = NO;
NSString *encryptedStr = [rsaEncryptor EncryptStringENC: plainText bUsePrivateKey: usePrivateKey];
NSLog(@"%@",encryptedStr);

// Now decrypt:
CkoRsa *rsaDecryptor = [[CkoRsa alloc] init];

rsaDecryptor.EncodingMode = @"hex";
success = [rsaDecryptor ImportPrivateKey: privateKey];

usePrivateKey = YES;
NSString *decryptedStr = [rsaDecryptor DecryptStringENC: encryptedStr bUsePrivateKey: usePrivateKey];

NSLog(@"%@",decryptedStr);