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Encrypt File to PKCS7 .p7m

See more Encryption Examples

_LANGUAGE_ example to public-key encrypt a file creating a PKCS#7 .p7m file as output. Also demonstrates how to decrypt the .p7m to recover the original file. Zig

const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

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

    const crypt = try chilkat.Crypt2.init();
    defer crypt.deinit();

    // Indicate the public-key encryption is to be used.
    // Do this by setting the encryption algorithm equal
    // to "PKI" (an acroynm for public-key infrastructure).
    crypt.setCryptAlgorithm("PKI");

    // Indicate the inner symmetric encryption algorithm to be used.
    // possible values are "aes", "des", "3des", and "rc2".
    // For this example, we'll use 256-bit AES encryption.
    crypt.setPkcs7CryptAlg("aes");
    crypt.setKeyLength(256);

    // To encrypt, only a certificate w/ public key is needed.
    // (The certificate w/ private key is required for decryption.)

    // The LoadFromFile method can load virtually any certificate format:
    // 1. DER encoded binary X.509 (.CER)
    // 2. Base-64 encoded X.509 (.CER)
    // 3. Cryptographic Message Syntax Standard - PKCS #7 Certificates (.P7B)
    // 4. PEM format
    const encrypt_cert = try chilkat.Cert.init();
    defer encrypt_cert.deinit();
    encrypt_cert.loadFromFile("/Users/chilkat/testData/cer/acme.cer") catch {
        std.debug.print("{s}\n", .{try encrypt_cert.getLastErrorText(alloc)});
        return;
    };

    // Tell the crypt object to use the certificate for encrypting:
    crypt.addEncryptCert(encrypt_cert);

    // Encrypt a file, producing a .p7m as output.
    // The input file is unchanged, the output .p7m contains the encrypted
    // contents of the input file.
    var in_file: [:0]const u8 = "/Users/chilkat/testData/pdf/sample.pdf";
    var out_file: [:0]const u8 = "/Users/chilkat/testData/p7m/sample.pdf.p7m";
    crypt.ckEncryptFile(in_file, out_file) catch {
        std.debug.print("{s}\n", .{try crypt.getLastErrorText(alloc)});
        return;
    };

    // For demonstration purposes, a different instance of the object will be used
    // for decryption.
    const decrypt = try chilkat.Crypt2.init();
    defer decrypt.deinit();

    // To decrypt, the certificate w/ private key is required.  A PFX (also known
    // as PKCS#12) is a common secure container for certs and private keys.
    const pfx_filename = "/Users/chilkat/testData/pfx/acme.pfx";
    const pfx_password = "secret";

    // Tell the component to look in the PFX file for certs and private keys.
    decrypt.addPfxSourceFile(pfx_filename, pfx_password) catch {
        std.debug.print("{s}\n", .{try decrypt.getLastErrorText(alloc)});
        return;
    };

    // Tell the decrypt object that PKI (public key encryption) is to be used
    // for decryptiong.
    decrypt.setCryptAlgorithm("PKI");
    // There is no need to set the Pkcs7Alg or KeyLength because this information
    // is contained within the .p7m

    // Decrypt the .p7m
    in_file = "/Users/chilkat/testData/p7m/sample.pdf.p7m";
    out_file = "/Users/chilkat/testData/pdf/recovered.pdf";
    decrypt.ckDecryptFile(in_file, out_file) catch {
        std.debug.print("{s}\n", .{try decrypt.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("Success!\n", .{});
}