Zig Requires Chilkat v11.0.0+

RSA-OAEP with SHA256 hashing

See more RSA Examples

RSA encrypt a SHA256 hash with OAEP padding. 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 pubkey = try chilkat.PublicKey.init();
    defer pubkey.deinit();

    const sb_pem = try chilkat.StringBuilder.init();
    defer sb_pem.deinit();
    const b_crlf = true;
    sb_pem.appendLine("-----BEGIN PUBLIC KEY-----", b_crlf) catch {};
    sb_pem.appendLine("MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA33TqqLR3eeUmDtHS89qF", b_crlf) catch {};
    sb_pem.appendLine("3p4MP7Wfqt2Zjj3lZjLjjCGDvwr9cJNlNDiuKboODgUiT4ZdPWbOiMAfDcDzlOxA", b_crlf) catch {};
    sb_pem.appendLine("04DDnEFGAf+kDQiNSe2ZtqC7bnIc8+KSG/qOGQIVaay4Ucr6ovDkykO5Hxn7OU7s", b_crlf) catch {};
    sb_pem.appendLine("Jp9TP9H0JH8zMQA6YzijYH9LsupTerrY3U6zyihVEDXXOv08vBHk50BMFJbE9iwF", b_crlf) catch {};
    sb_pem.appendLine("wnxCsU5+UZUZYw87Uu0n4LPFS9BT8tUIvAfnRXIEWCha3KbFWmdZQZlyrFw0buUE", b_crlf) catch {};
    sb_pem.appendLine("f0YN3/Q0auBkdbDR/ES2PbgKTJdkjc/rEeM0TxvOUf7HuUNOhrtAVEN1D5uuxE1W", b_crlf) catch {};
    sb_pem.appendLine("SwIDAQAB", b_crlf) catch {};
    sb_pem.appendLine("-----END PUBLIC KEY-----", b_crlf) catch {};

    // Load the public key object from the PEM.
    pubkey.loadFromString(try sb_pem.getAsString(alloc)) catch {
        std.debug.print("{s}\n", .{try pubkey.getLastErrorText(alloc)});
        return;
    };

    // Build a small string to encrypt
    const json = try chilkat.JsonObject.init();
    defer json.deinit();
    json.updateString("example", "123") catch {};
    json.updateString("hello", "world") catch {};
    std.debug.print("{s}\n", .{try json.emit(alloc)});

    // This is the JSON to be RSA encrypted:  {"example":"123","hello":"world"}

    // IMPORTANT: RSA encryption is only used to encrypt small amounts of data.
    // RSA is only able to encrypt data to a maximum amount of your key size (2048 bits = 256 bytes)
    // minus padding / header data (11 bytes for PKCS#1 v1.5 padding, 42 bytes for OAEP).
    // As a result it is often not possible to encrypt files with RSA directly.
    // RSA is also not meant for this purpose.
    //
    // If you want to encrypt more data, you can use something like:
    // 1) Generate a 256-bit random keystring K
    // 2) Encrypt your data with AES-CBC with K
    // 3) Encrypt K with RSA
    // 4) Send both to the other side

    const rsa = try chilkat.Rsa.init();
    defer rsa.deinit();
    rsa.setPkcsPadding(false);
    rsa.setOaepHash("SHA-256");
    rsa.usePublicKey(pubkey) catch {};
    rsa.setEncodingMode("base64");

    // Note: The OAEP padding uses random bytes in the padding, and therefore each time encryption happens,
    // even using the same data and key, the result will be different --  but still valid.  One should not expect
    // to get the same output.
    const b_use_private_key = false;
    const encrypted_str = rsa.encryptStringENC(alloc, try json.emit(alloc), b_use_private_key) catch {
        std.debug.print("{s}\n", .{try rsa.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("Result: {s}\n", .{encrypted_str});
}