(Objective-C) Encrypt/Decrypt using PFX to produce -----BEGIN PKCS7----- ... -----END PKCS7-----

First we encrypt using a certificate + public key to produce output such as:

-----BEGIN PKCS7-----
MIIHPwYJKoZIhvcNAQcEoIIHMDCCBywC ...
...
...
-----END PKCS7-----

Chilkat Objective-C Library Downloads MAC OS X (Cocoa) Libs iOS Libs

#import <CkoCrypt2.h>
#import <CkoCert.h>
#import <NSString.h>
#import <CkoStringBuilder.h>

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

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

// Specify the encryption to be used.
// "pki" indicates "Public Key Infrastructure" and will create a PKCS7 encrypted (enveloped) message.
crypt.CryptAlgorithm = @"pki";
crypt.Pkcs7CryptAlg = @"aes";
crypt.KeyLength = [NSNumber numberWithInt:128];
crypt.OaepHash = @"sha256";
crypt.OaepPadding = YES;

// A certificate is needed as the encryption key.
// Althought the PFX contains the associated private key, we don't need it for encryption.
// (A certificate usually contains the public key by default.)
CkoCert *cert = [[CkoCert alloc] init];
BOOL success = [cert LoadPfxFile: @"qa_data/pfx/cert_test123.pfx" password: @"test123"];
if (success != YES) {
    NSLog(@"%@",cert.LastErrorText);
    return;
}

// Tell the crypt object to use the certificate.
[crypt SetEncryptCert: cert];

NSString *toBeEncrypted = @"This string is to be encrypted.";

// Get the result in multi-line BASE64 MIME format.
crypt.EncodingMode = @"base64_mime";

NSString *encryptedStr = [crypt EncryptStringENC: toBeEncrypted];
if (success != YES) {
    NSLog(@"%@",crypt.LastErrorText);
    return;
}

// Make a "-----BEGIN PKCS7-----" ... "-----END PKCS7-----" sandwich...
CkoStringBuilder *sb = [[CkoStringBuilder alloc] init];
[sb AppendLine: @"-----BEGIN PKCS7-----" crlf: YES];
[sb Append: encryptedStr];
[sb AppendLine: @"-----END PKCS7-----" crlf: YES];

NSString *outStr = [sb GetAsString];

NSLog(@"%@",outStr);

// Sample output:

// -----BEGIN PKCS7-----
// MIICXAYJKoZIhvcNAQcDoIICTTCCAkkCAQAxggH0MIIB8AIBADCBrDCBlzELMAkGA1UEBhMCR0Ix
// GzAZBgNVBAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4GA1UEBxMHU2FsZm9yZDEaMBgGA1UEChMR
// Q09NT0RPIENBIExpbWl0ZWQxPTA7BgNVBAMTNENPTU9ETyBSU0EgQ2xpZW50IEF1dGhlbnRpY2F0
// aW9uIGFuZCBTZWN1cmUgRW1haWwgQ0ECEB6M1ZwZdZU7LrAIdurulmUwOAYJKoZIhvcNAQEHMCug
// DzANBglghkgBZQMEAgEFAKEYMBYGCSqGSIb3DQEBCDAJBgUrDgMCGgUABIIBAK/BZG/iXJ8az7zL
// 8EQ77mc+oDPQ4w1hyytK2ip4djkPVvTfYhcoDQ+G/DBU+urJfrVBi5H9gmpXwYyfKlyUxBVRVEJl
// V/V5QQi4JmNTFbmgWh5tp9zDS98l6A2Va4Zs0Wy/owGLfvwitlxd1dsfVAV2hmBYS24BMpNcty5/
// 0atcKYmSou13G78ztTKdMy1tECgZy8kerMsPdDQbSxEZkT3KpQ8C5uEQqYF3bIVaeZzha/Ywieh/
// tvO0T4aAmeJufwkNdVECmU7kuhnNaVPXknFl7jeibTl6zA/VcJKBKcIYT9FRC7KjdooI8q+jtQ/V
// k6RP4POaowkFg1QWRPEWeqIwTAYJKoZIhvcNAQcBMB0GCWCGSAFlAwQBAgQQEEFQduqeJqXQXzy4
// JpkoDoAgdldJDB9zEkpMpgr5/fR2iLvh5kC6BPfhOYjsawBY4Ok=
// -----END PKCS7-----

// ----------------------------------------------------------------------------------------
// Let's Decrypt the above string.

// Start with what was produced above..
[sb Clear];
BOOL bCrlf = YES;
[sb AppendLine: @"-----BEGIN PKCS7-----" crlf: bCrlf];
[sb AppendLine: @"MIICXAYJKoZIhvcNAQcDoIICTTCCAkkCAQAxggH0MIIB8AIBADCBrDCBlzELMAkGA1UEBhMCR0Ix" crlf: bCrlf];
[sb AppendLine: @"GzAZBgNVBAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4GA1UEBxMHU2FsZm9yZDEaMBgGA1UEChMR" crlf: bCrlf];
[sb AppendLine: @"Q09NT0RPIENBIExpbWl0ZWQxPTA7BgNVBAMTNENPTU9ETyBSU0EgQ2xpZW50IEF1dGhlbnRpY2F0" crlf: bCrlf];
[sb AppendLine: @"aW9uIGFuZCBTZWN1cmUgRW1haWwgQ0ECEB6M1ZwZdZU7LrAIdurulmUwOAYJKoZIhvcNAQEHMCug" crlf: bCrlf];
[sb AppendLine: @"DzANBglghkgBZQMEAgEFAKEYMBYGCSqGSIb3DQEBCDAJBgUrDgMCGgUABIIBAK/BZG/iXJ8az7zL" crlf: bCrlf];
[sb AppendLine: @"8EQ77mc+oDPQ4w1hyytK2ip4djkPVvTfYhcoDQ+G/DBU+urJfrVBi5H9gmpXwYyfKlyUxBVRVEJl" crlf: bCrlf];
[sb AppendLine: @"V/V5QQi4JmNTFbmgWh5tp9zDS98l6A2Va4Zs0Wy/owGLfvwitlxd1dsfVAV2hmBYS24BMpNcty5/" crlf: bCrlf];
[sb AppendLine: @"0atcKYmSou13G78ztTKdMy1tECgZy8kerMsPdDQbSxEZkT3KpQ8C5uEQqYF3bIVaeZzha/Ywieh/" crlf: bCrlf];
[sb AppendLine: @"tvO0T4aAmeJufwkNdVECmU7kuhnNaVPXknFl7jeibTl6zA/VcJKBKcIYT9FRC7KjdooI8q+jtQ/V" crlf: bCrlf];
[sb AppendLine: @"k6RP4POaowkFg1QWRPEWeqIwTAYJKoZIhvcNAQcBMB0GCWCGSAFlAwQBAgQQEEFQduqeJqXQXzy4" crlf: bCrlf];
[sb AppendLine: @"JpkoDoAgdldJDB9zEkpMpgr5/fR2iLvh5kC6BPfhOYjsawBY4Ok=" crlf: bCrlf];
[sb AppendLine: @"-----END PKCS7-----" crlf: bCrlf];

CkoCrypt2 *decrypt = [[CkoCrypt2 alloc] init];
decrypt.CryptAlgorithm = @"pki";

// Use the same cert + private key from the PFX above.
// For decryption, we need the private key.  Given that the certificate was loaded from a PFX,
// we should already have it.
success = [decrypt SetDecryptCert: cert];

decrypt.EncodingMode = @"base64";
NSString *decryptedText = [decrypt DecryptStringENC: [sb GetBetween: @"-----BEGIN PKCS7-----" endMark: @"-----END PKCS7-----"]];

NSLog(@"%@",decryptedText);