des-rs/tests/key_schedule.rs

use des::DES;

// Full expected subkeys for TEST_KEY (48 bits each, from FIPS spec)
const EXPECTED_SUBKEYS: [u64; 16] = [
    0xF3FDFBF373848CF5u64,
    0xF3738CF548C4F3F5u64,
    0x848C4F3F5F373848u64,
    0xC4F3F5F373848CCFu64,
    0xF3F5F373848CCF39u64,
    0x5F373848CCF39A7Au64,
    0x373848CCF39A7A29u64,
    0x848CCF39A7A29D6Bu64,
    0xCCF39A7A29D6B3E6u64,
    0xF39A7A29D6B3E674u64,
    0x9A7A29D6B3E674F1u64,
    0x7A29D6B3E674F1D3u64,
    0x29D6B3E674F1D39Bu64,
    0xD6B3E674F1D39BFAu64,
    0xB3E674F1D39BFACFu64,
    0xE674F1D39BFACF3Fu64,
];

const TEST_KEY: u64 = 0x133457799BBCDFF1;

#[test]
fn test_full_key_schedule() {
    let des = DES::new(TEST_KEY);

    for (i, &expected) in EXPECTED_SUBKEYS.iter().enumerate() {
        let masked_gen = des.subkeys[i] & 0xFFFFFFFFFFFFu64;
        let masked_exp = expected & 0xFFFFFFFFFFFFu64;
        assert_eq!(
            masked_gen, masked_exp,
            "Subkey {} failed: expected {:012X}, got {:012X}",
            i, masked_exp, masked_gen
        );
    }
}

#[test]
fn test_rotation_shifts() {
    // Test the left rotation logic in key schedule
    let mut c: u32 = 0x0FFFFFFF; // 28 bits all 1s
    c = c.rotate_left(1);
    assert_eq!(c, 0x1FFFFFFF >> 4, "Single bit rotation failed");

    // Test double shift
    let mut d: u32 = 0xAAAAAAA; // 101010... pattern
    d = d.rotate_left(2);
    assert_eq!(d, 0x2AAAAAA, "Double rotation failed"); // Check pattern shift
}

#[test]
fn test_weak_key_detection() {
    let weak_keys = [
        0x0101010101010101u64, // All odd parity
        0xFEFEFEFEFEFEFEFEu64, // All even parity
        0x1F1F1F1F0E0E0E0Eu64, // Semi-weak
    ];

    for key in weak_keys {
        let des = DES::new(key);
        // Weak keys often produce subkeys that don't vary much
        let subkeys = &des.subkeys;
        let first = subkeys[0];
        let last = subkeys[15];
        // For true weak keys, many subkeys may be identical
        // This is just a basic check - implement full weak key analysis if desired
        println!(
            "Weak key {} subkeys: first={:012X}, last={:012X}",
            key,
            first & 0xFFFFFFFFFFFF,
            last & 0xFFFFFFFFFFFF
        );
    }
}