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Compute JWK Thumbprint for RSA and EC Public Keys

See more ECC Examples

Demonstrates how to compute a JSON Web Key thumbprint for a public key (RSA or ECC).

Note: This example requires Chilkat v9.5.0.66 or greater.

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

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

    const pub_key = try chilkat.PublicKey.init();
    defer pub_key.deinit();

    // A public key can be loaded from any format (binary DER, PEM, etc.)
    // This example will load the public keys from JWK format,
    // and will then compute the JWK thumbprint.

    // First do it for an RSA public key...

    const sb = try chilkat.StringBuilder.init();
    defer sb.deinit();
    sb.append("{") catch {};
    sb.append("\"kty\": \"RSA\",") catch {};
    sb.append("\"n\": \"0vx7agoebGcQSuuPiLJXZptN9nndrQmbXEps2aiAFbWhM78LhWx4cbbfAAt") catch {};
    sb.append("VT86zwu1RK7aPFFxuhDR1L6tSoc_BJECPebWKRXjBZCiFV4n3oknjhMstn6") catch {};
    sb.append("4tZ_2W-5JsGY4Hc5n9yBXArwl93lqt7_RN5w6Cf0h4QyQ5v-65YGjQR0_FD") catch {};
    sb.append("W2QvzqY368QQMicAtaSqzs8KJZgnYb9c7d0zgdAZHzu6qMQvRL5hajrn1n9") catch {};
    sb.append("1CbOpbISD08qNLyrdkt-bFTWhAI4vMQFh6WeZu0fM4lFd2NcRwr3XPksINH") catch {};
    sb.append("aQ-G_xBniIqbw0Ls1jF44-csFCur-kEgU8awapJzKnqDKgw\",") catch {};
    sb.append("\"e\": \"AQAB\",") catch {};
    sb.append("\"alg\": \"RS256\",") catch {};
    sb.append("\"kid\": \"2011-04-29\"") catch {};
    sb.append("}") catch {};

    // The JWK format is automatically detected..
    pub_key.loadFromString(try sb.getAsString(alloc)) catch {
        std.debug.print("{s}\n", .{try pub_key.getLastErrorText(alloc)});
        return;
    };

    // Get the JWK thumbprint (using SHA256)
    std.debug.print("JWK thumbprint: {s}\n", .{try pub_key.getJwkThumbprint(alloc, "SHA256")});

    // Output:
    // JWK thumbprint: NzbLsXh8uDCcd-6MNwXF4W_7noWXFZAfHkxZsRGC9Xs

    // --------------------------------------------------------------
    // Now let's do an EC public key:
    sb.clear();
    sb.append("{ ") catch {};
    sb.append("  \"kty\": \"EC\",") catch {};
    sb.append("  \"crv\": \"P-256\",") catch {};
    sb.append("  \"x\": \"tDeeYABgKEAbWicYPCEEI8sP4SRIhHKcHDW7VqrB4LA\",") catch {};
    sb.append("  \"y\": \"J08HOoIZ0rX2Me3bNFZUltfxIk1Hrc8FsLu8VaSxsMI\"") catch {};
    sb.append("}") catch {};

    pub_key.loadFromString(try sb.getAsString(alloc)) catch {
        std.debug.print("{s}\n", .{try pub_key.getLastErrorText(alloc)});
        return;
    };

    // Get the JWK thumbprint (using SHA256)
    std.debug.print("JWK thumbprint: {s}\n", .{try pub_key.getJwkThumbprint(alloc, "SHA256")});

    // Output:
    // JWK thumbprint: 8fm8079s3nu4FLV_7dVJoJ69A8XCXn7Za2mtaWCnxR4
}