Zig

ECDSA Sign Data and Verify Signature

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Demonstrates using the Elliptic Curve Digital Signature Algorithm to hash data and sign it. Also demonstrates how to verify the ECDSA signature. 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.

    // To create an ECDSA signature, the data first needs to be hashed.  Then the hash
    // is signed.

    // Use Chilkat Crypt2 to generate a hash for any of the following
    // hash algorithms: SHA256, SHA384, SHA512, SHA1, MD5, MD2, HAVAL, RIPEMD128/160/256/320

    const crypt = try chilkat.Crypt2.init();
    defer crypt.deinit();
    crypt.setHashAlgorithm("SHA256");
    crypt.setCharset("utf-8");
    crypt.setEncodingMode("base64");

    // Hash a string.
    const hash1 = try crypt.hashStringENC(alloc, "The quick brown fox jumps over the lazy dog");
    std.debug.print("hash1 = {s}\n", .{hash1});

    // Or hash a file..
    const hash2 = try crypt.hashFileENC(alloc, "qa_data/hamlet.xml");
    std.debug.print("hash2 = {s}\n", .{hash2});

    // (The Crypt2 API provides many other ways to hash data..)

    // -----------------------------------------------------------
    // An ECDSA private key is used for signing.  The public key is for signature verification.
    // Load our ECC private key.
    // Our private key file contains this:

    //     // -----BEGIN PRIVATE KEY-----
    //     MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQg3J8q/24D1sEKGdP9
    //     72MGYElLGpw/a56Y3t6pfON3uhShRANCAATlSmoizyhAwoYZAOuFBATl07/1RR54
    //     a1Dzfm16grxJe666AGKR+bSs24hk7TEpaeCTvT8YOOM3l+xKFg7zq6Q9
    //     -----END PRIVATE KEY-----

    const priv_key = try chilkat.PrivateKey.init();
    defer priv_key.deinit();
    priv_key.loadPemFile("qa_data/ecc/secp256r1-key-pkcs8.pem") catch {
        std.debug.print("{s}\n", .{try priv_key.getLastErrorText(alloc)});
        return;
    };

    // We'll need a PRNG source for random number generation.
    // Use Chilkat's PRNG (for the Fortuna PRNG algorithm).
    const prng = try chilkat.Prng.init();
    defer prng.deinit();

    // Sign the hash..
    const ecdsa = try chilkat.Ecc.init();
    defer ecdsa.deinit();
    const ecdsa_sig_base64 = ecdsa.signHashENC(alloc, hash1, "base64", priv_key, prng) catch {
        std.debug.print("{s}\n", .{try ecdsa.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("ECDSA signature = {s}\n", .{ecdsa_sig_base64});

    // -----------------------------------------------------------
    // Now let's verify the signature using the public key.

    const pub_key = try chilkat.PublicKey.init();
    defer pub_key.deinit();
    pub_key.loadFromFile("qa_data/ecc/secp256r1-pubkey.pem") catch {
        std.debug.print("{s}\n", .{try pub_key.getLastErrorText(alloc)});
        return;
    };

    const result = ecdsa.verifyHashENC(hash1, ecdsa_sig_base64, "base64", pub_key);
    if (result == 1) {
        std.debug.print("Signature is valid.\n", .{});
        return;
    }

    if (result == 0) {
        std.debug.print("Signature is invalid.\n", .{});
        return;
    }

    if (result < 0) {
        std.debug.print("{s}\n", .{try ecdsa.getLastErrorText(alloc)});
        std.debug.print("The VerifyHashENC method call failed.\n", .{});
        return;
    }
}