Zig Requires Chilkat v11.0.0+

About RSA Public/Private Keys

See more RSA Examples

This example provides some additional information for understanding public/private key pairs. In demonstrates how a private key is a superset of the public key. A public key contains the modulus and exponent. The matching private key also contains the modulus and exponent, but also contains the additional private key parts. Zig

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

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

    const cert = try chilkat.Cert.init();
    defer cert.deinit();

    // Load a digital certificate.
    cert.loadFromFile("digitalCert.cer") catch {
        std.debug.print("{s}\n", .{try cert.getLastErrorText(alloc)});
        return;
    };

    // A .cer file does not contain the private key.  It should contain
    // the public key...
    const pub_key = try chilkat.PublicKey.init();
    defer pub_key.deinit();
    cert.getPublicKey(pub_key) catch {};

    // Let's have a look at it (in XML format).
    std.debug.print("Public Key from Certificate:\n", .{});
    std.debug.print("{s}\n", .{try pub_key.getXml(alloc)});

    // An RSA public key consists of a modulus and exponent.

    // An RSA private key includes both the modulus and exponent,
    // as well as other "big" numbers: P, Q, D, etc.

    // Let's load an RSA private key from a DER-encoded file:
    const priv_key = try chilkat.PrivateKey.init();
    defer priv_key.deinit();

    priv_key.loadAnyFormatFile("PrivateKey.key", "") catch {
        std.debug.print("{s}\n", .{try priv_key.getLastErrorText(alloc)});
        return;
    };

    // If this private key is the matching half to the public key from
    // the certificate, then the modulus and exponent should
    // be identical.  (Thus, a "private key" really contains both the public part as well as the private parts...).
    std.debug.print("Private Key from DER:\n", .{});
    std.debug.print("{s}\n", .{try priv_key.getXml(alloc)});
}