Objective-C

Encrypt a file to a PKCS7 encrypted message using multiple certificates from different users

See more Encryption Examples

Demonstrates how to encrypt a file to a PKCS7 encrypted message using multiple certificates from different users. Any one of the users can decrypt using his/her own certificate + private key.

Note: When doing public key encryption, it is the public key that is used to encrypt. The private key is required for decryption.

Objective-C

#import <CkoCrypt2.h>
#import <CkoCert.h>
#import <CkoBinData.h>

BOOL success = NO;

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

CkoCrypt2 *crypt = [[CkoCrypt2 alloc] init];

//  Tell the crypt object to use 3 certificates.
//  Do this by calling AddEncryptCert for each certificate.

//  Load a digital certificate. 
//  We don't need the private key for encryption.
//  Only the public key is needed (which is included in a certificate).
CkoCert *cert1 = [[CkoCert alloc] init];
success = [cert1 LoadFromFile: @"qa_data/user1/cert_user1.pem"];
//  Assume success for the example, but make sure your application checks for success/failure...
[crypt AddEncryptCert: cert1];

CkoCert *cert2 = [[CkoCert alloc] init];
success = [cert2 LoadFromFile: @"qa_data/user2/cert_user2.pem"];
[crypt AddEncryptCert: cert2];

CkoCert *cert3 = [[CkoCert alloc] init];
success = [cert3 LoadFromFile: @"qa_data/user3/cert_user3.pem"];
[crypt AddEncryptCert: cert3];

//  Indicate that we want PKI encryption (i.e. public-key infrastructure)
//  to produce a CMS message (Cryptographic Message Syntax/PKCS7),
//  that is be created with RSAES-OAEP padding, SHA256, and AES-128 for the
//  bulk encryption.
crypt.CryptAlgorithm = @"pki";
crypt.Pkcs7CryptAlg = @"aes";
crypt.KeyLength = [NSNumber numberWithInt:128];
crypt.OaepHash = @"sha256";
crypt.OaepPadding = YES;

//  Load the file to be encrypted...
CkoBinData *fileData = [[CkoBinData alloc] init];
success = [fileData LoadFile: @"qa_data/jpg/penguins.jpg"];
//  Your app should check for success/failure..

//  Encrypt the data.  The contents of the fileData object are replaced with the PKCS7 encrypted message.
success = [crypt EncryptBd: fileData];
if (success != YES) {
    NSLog(@"%@",crypt.LastErrorText);
    return;
}

//  Save the PKCS7 encrypted message to a file..
success = [fileData WriteFile: @"qa_output/pkcs7_encrypted.p7"];

//  Now indicate that the PKCS7 output is to be returned in the base64 encoding.
crypt.EncodingMode = @"base64";

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