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AES XTS Mode

See more Encryption Examples

Demonstrates the AES-XTS mode of operation.

Note: This example requires Chilkat v9.5.0.91 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();

    // This example assumes the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // Here we have a sample from CAVS validatition data:

    // COUNT = 301
    // DataUnitLen = 200
    // Key =
    // 394c97881abd989d29c703e48a72b397
    // a7acf51b59649eeea9b33274d8541df4
    // i = 4b15c684a152d485fe9937d39b168c29
    // PT = 2f3b9dcfbae729583b1d1ffdd16bb6fe2757329435662a78f0
    // CT = f3473802e38a3ffef4d4fb8e6aa266ebde553a64528a06463e

    // Note: The above sample requires an AES-XTS implementation that fully supports ciphertext-stealing
    // because the data to be encrypted is not an even multiple of the AES block size (i.e. not a multiple of 16 bytes).
    // Chilkat fully supports AES-XTS with ciphertext stealing.
    // (i.e. Chilkat implements XEX-based tweaked-codebook mode with ciphertext stealing (XTS))

    const key = "394c97881abd989d29c703e48a72b397";
    const tweak_key = "a7acf51b59649eeea9b33274d8541df4";
    const data_unit = "4b15c684a152d485fe9937d39b168c29";

    const bd = try chilkat.BinData.init();
    defer bd.deinit();
    bd.appendEncoded("2f3b9dcfbae729583b1d1ffdd16bb6fe2757329435662a78f0", "hex") catch {};

    const crypt = try chilkat.Crypt2.init();
    defer crypt.deinit();

    crypt.setCryptAlgorithm("aes");
    crypt.setCipherMode("xts");
    crypt.setKeyLength(128);

    crypt.setEncodedKey(key, "hex");
    crypt.xtsSetEncodedTweakKey(tweak_key, "hex");
    crypt.xtsSetEncodedTweakValue(data_unit, "hex");

    // In-place encrypt the contents of bd.
    try crypt.encryptBd(bd);

    std.debug.print("CT = {s}\n", .{try bd.getEncoded(alloc, "hexlower")});

    // Decrypt to revert back to the unencrypted content:
    try crypt.decryptBd(bd);

    std.debug.print("PT = {s}\n", .{try bd.getEncoded(alloc, "hexlower")});

    // Output:
    // CT = f3473802e38a3ffef4d4fb8e6aa266ebde553a64528a06463e
    // PT = 2f3b9dcfbae729583b1d1ffdd16bb6fe2757329435662a78f0
}