(Objective-C) RSA Encrypt RSA/ECB/OAEPWithSHA1AndMGF1Padding

Demonstrates how to RSA encrypt using RSA/ECB/OAEPWithSHA1AndMGF1Padding. Also demonstrates RSA/ECB/OAEPWithSHA-256AndMGF1Padding. Both of these terms are from Java's JCE. Note: In this context, "ECB" doesn't actually mean anything. It's a symmetric cipher mode that doesn't apply (or make sense) in this context.

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

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

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

// First load a public key object with a public key.
// In this case, we'll load it from a file.
CkoPublicKey *pubkey = [[CkoPublicKey alloc] init];
BOOL success = [pubkey LoadFromFile: @"qa_data/pem/rsa_public.pem"];
if (success != YES) {
    NSLog(@"%@",pubkey.LastErrorText);
    return;
}

// RSA encryption is limited to small amounts of data. The limit
// is typically a few hundred bytes and is based on the key size and
// padding (OAEP vs. PKCS1_5).  RSA encryption is typically used for
// encrypting hashes or symmetric (bulk encryption algorithm) secret keys.
NSString *plainText = @"Time is an illusion. Lunchtime doubly so.";

// Import the public key to be used for encrypting.
success = [rsa ImportPublicKeyObj: pubkey];

// To get OAEP padding, set the OaepPadding property:
rsa.OaepPadding = YES;

// To use SHA1 or SHA-256, set the OaepHash property
rsa.OaepHash = @"sha256";
// for SHA1 --
rsa.OaepHash = @"sha1";

// Indicate we'll want hex output
rsa.EncodingMode = @"hex";

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

// -------------------------------------------------
// Now decrypt with the matching private key.
CkoRsa *rsa2 = [[CkoRsa alloc] init];

CkoPrivateKey *privKey = [[CkoPrivateKey alloc] init];
success = [privKey LoadEncryptedPem: @"qa_data/pem/rsa_passwd.pem" password: @"passwd"];
if (success != YES) {
    NSLog(@"%@",privKey.LastErrorText);
    return;
}

success = [rsa2 ImportPrivateKeyObj: privKey];

// Make sure we have the same settings used for encryption.
rsa2.OaepPadding = YES;
rsa2.EncodingMode = @"hex";
rsa2.OaepHash = @"sha1";

NSString *originalStr = [rsa2 DecryptStringENC: encryptedStr bUsePrivateKey: YES];

NSLog(@"%@",originalStr);