ab_riscv_interpreter/rv32/zk/zkn/zknd/

rv32_zknd_helpers.rs

//! Opaque helpers for RV32 Zknd extension

use ab_riscv_primitives::prelude::*;

/// AES forward S-box (SubBytes, used only for the key schedule)
#[cfg(not(all(
    not(miri),
    all(
        any(target_arch = "riscv32", target_arch = "riscv64"),
        any(target_feature = "zknd", target_feature = "zkne")
    )
)))]
#[rustfmt::skip]
pub(crate) const SBOX: [u8; 256] = [
    0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b,
    0xfe, 0xd7, 0xab, 0x76, 0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0,
    0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, 0xb7, 0xfd, 0x93, 0x26,
    0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
    0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2,
    0xeb, 0x27, 0xb2, 0x75, 0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0,
    0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, 0x53, 0xd1, 0x00, 0xed,
    0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
    0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f,
    0x50, 0x3c, 0x9f, 0xa8, 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5,
    0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, 0xcd, 0x0c, 0x13, 0xec,
    0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
    0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14,
    0xde, 0x5e, 0x0b, 0xdb, 0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c,
    0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, 0xe7, 0xc8, 0x37, 0x6d,
    0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
    0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f,
    0x4b, 0xbd, 0x8b, 0x8a, 0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e,
    0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e, 0xe1, 0xf8, 0x98, 0x11,
    0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
    0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f,
    0xb0, 0x54, 0xbb, 0x16,
];

/// AES inverse S-box (InvSubBytes)
#[cfg(not(all(
    not(miri),
    any(target_arch = "riscv32", target_arch = "riscv64"),
    target_feature = "zknd"
)))]
#[rustfmt::skip]
pub(crate) const INV_SBOX: [u8; 256] = [
    0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e,
    0x81, 0xf3, 0xd7, 0xfb, 0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87,
    0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb, 0x54, 0x7b, 0x94, 0x32,
    0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
    0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49,
    0x6d, 0x8b, 0xd1, 0x25, 0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16,
    0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92, 0x6c, 0x70, 0x48, 0x50,
    0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
    0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05,
    0xb8, 0xb3, 0x45, 0x06, 0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02,
    0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b, 0x3a, 0x91, 0x11, 0x41,
    0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
    0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8,
    0x1c, 0x75, 0xdf, 0x6e, 0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89,
    0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b, 0xfc, 0x56, 0x3e, 0x4b,
    0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
    0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59,
    0x27, 0x80, 0xec, 0x5f, 0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d,
    0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef, 0xa0, 0xe0, 0x3b, 0x4d,
    0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
    0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63,
    0x55, 0x21, 0x0c, 0x7d,
];

#[cfg(any(
    test,
    not(all(
        not(miri),
        all(
            any(target_arch = "riscv32", target_arch = "riscv64"),
            any(target_feature = "zknd", target_feature = "zkne")
        )
    ))
))]
#[inline(always)]
pub(crate) fn gmul(mut a: u8, mut b: u8) -> u8 {
    let mut p = 0u8;
    for _ in 0..8 {
        if b & 1 != 0 {
            p ^= a;
        }
        let carry = a >> 7;
        a <<= 1;
        if carry != 0 {
            a ^= 0x1b;
        }
        b >>= 1;
    }
    p
}

/// Software fallback for aes32dsi and aes32dsmi.
///
/// Both instructions share the same S-box and MixColumn machinery; the only difference is whether
/// InvMixColumns is applied.
#[cfg(not(all(not(miri), target_arch = "riscv32", target_feature = "zknd")))]
pub(in super::super) mod soft {
    use crate::rv32::zk::zkn::zknd::rv32_zknd_helpers::{INV_SBOX, gmul};

    /// Compute the partial InvMixColumns contribution for a single substituted byte `b`.
    ///
    /// This is `aes_mixcolumn_byte_inv` from the Sail reference:
    /// the four output bytes of InvMixColumns when the input column has `b` in one position and
    /// zeros elsewhere - packed into a little-endian `u32`.
    ///
    /// Column matrix multiply for InvMixColumns:
    /// ```text
    /// r0 = 0x0e*b
    /// r1 = 0x09*b
    /// r2 = 0x0d*b
    /// r3 = 0x0b*b
    /// ```
    #[inline(always)]
    pub(super) fn inv_mix_col_byte(b: u8) -> u32 {
        let r0 = u32::from(gmul(b, 0x0e));
        let r1 = u32::from(gmul(b, 0x09));
        let r2 = u32::from(gmul(b, 0x0d));
        let r3 = u32::from(gmul(b, 0x0b));
        r0 | (r1 << 8) | (r2 << 16) | (r3 << 24)
    }

    /// `aes32dsi rs1, rs2, bs`
    ///
    /// Pseudocode:
    /// ```text
    /// shamt = bs * 8
    /// si    = (rs2 >> shamt) & 0xff
    /// so    = INV_SBOX[si] as u32
    /// rd    = rs1 ^ rol32(so, shamt)
    /// ```
    #[inline(always)]
    pub(super) fn aes32dsi(rs1: u32, rs2: u32, bs: u8) -> u32 {
        let shamt = u32::from(bs) * 8;
        let si = ((rs2 >> shamt) & 0xff) as u8;
        let so = u32::from(INV_SBOX[usize::from(si)]);
        rs1 ^ so.rotate_left(shamt)
    }

    /// `aes32dsmi rs1, rs2, bs`
    ///
    /// Pseudocode:
    /// ```text
    /// shamt = bs * 8
    /// si    = (rs2 >> shamt) & 0xff
    /// so    = INV_SBOX[si]
    /// mixed = inv_mix_col_byte(so)
    /// rd    = rs1 ^ rol32(mixed, shamt)
    /// ```
    #[inline(always)]
    pub(super) fn aes32dsmi(rs1: u32, rs2: u32, bs: u8) -> u32 {
        let shamt = u32::from(bs) * 8;
        let si = ((rs2 >> shamt) & 0xff) as u8;
        let so = INV_SBOX[usize::from(si)];
        let mixed = inv_mix_col_byte(so);
        rs1 ^ mixed.rotate_left(shamt)
    }
}

#[inline(always)]
#[doc(hidden)]
pub fn aes32dsi(rs1: u32, rs2: u32, bs: Rv32AesBs) -> u32 {
    // TODO: Miri is excluded because corresponding intrinsic is not implemented there
    cfg_select! {
        all(
            not(miri),
            target_arch = "riscv32",
            target_feature = "zknd"
        ) => {
            // SAFETY: Compile-time checked for supported feature
            unsafe {
                core::arch::riscv32::aes32dsi(rs1, rs2, u8::from(bs))
            }
        }
        _ => { soft::aes32dsi(rs1, rs2, u8::from(bs)) }
    }
}

#[inline(always)]
#[doc(hidden)]
pub fn aes32dsmi(rs1: u32, rs2: u32, bs: Rv32AesBs) -> u32 {
    // TODO: Miri is excluded because corresponding intrinsic is not implemented there
    cfg_select! {
        all(
            not(miri),
            target_arch = "riscv32",
            target_feature = "zknd"
        ) => {
            // SAFETY: Compile-time checked for supported feature
            unsafe {
                core::arch::riscv32::aes32dsmi(rs1, rs2, u8::from(bs))
            }
        }
        _ => { soft::aes32dsmi(rs1, rs2, u8::from(bs)) }
    }
}