Zig

CMS Sign Hash

Demonstrates how to use the SignHashENC method to sign a pre-computed hash. This method creates a CMS signature (PKCS7 detached signature).

This example requires Chilkat v9.5.0.90 or later.

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();

    // Create the hash to be signed...
    crypt.setHashAlgorithm("sha256");
    crypt.setEncodingMode("base64");
    crypt.setCharset("utf-8");
    // Create the SHA256 hash of a string using the utf-8 byte representation.
    // Return the hash as base64.
    const base64_hash = try crypt.hashStringENC(alloc, "This is the string to be hashed");

    // Load a certificate for signing.
    const cert = try chilkat.Cert.init();
    defer cert.deinit();
    cert.loadPfxFile("qa_data/pfx/cert_test123.pfx", "test123") catch {
        std.debug.print("{s}\n", .{try cert.getLastErrorText(alloc)});
        return;
    };

    crypt.setSigningCert(cert) catch {};

    // Sign the hash to create a base64 CMS signature (which does not contain the original data).
    // We can get the signature in a single line of base64 by specifying "base64", or
    // we can get multi-line base64 by specifying "base64_mime".
    crypt.setEncodingMode("base64_mime");
    const base64_cms_sig = crypt.signHashENC(alloc, base64_hash, "sha256", "base64") catch {
        std.debug.print("{s}\n", .{try crypt.getLastErrorText(alloc)});
        return;
    };

    // Note: In the above call to SignHashENC, the encoding of the returned CMS signature is specified by the EncodingMode property.
    // However, the encoding of the passed-in hash is indicated by the 3rd argument.

    std.debug.print("CMS Signature: {s}\n", .{base64_cms_sig});
}