chore: uses sha256compression opcode in Noir and implements acvm solv…

…er for it (AztecProtocol#4511)

This PR should be merged **after** PR AztecProtocol#4503 , because it uses the opcode
implemented by the latter.

In this PR, I add the implementation of the ACVM solver for
sha256compression opcode, and use it in Noir implementation of sha256.

This gives us 3 ways of doing sha256. You can see below the resulting
circuit size for hashing 1 byte with each of them:

- The full Noir implementation : 17161 ACIR Opcodes, Circuit size is
65065
- The full BB implementation: 75 ACIR Opcodes, Circuit size is 38799
- Mixed Noir+sha256compression opcode: 351 ACIR Occodes, Circuit size is
15495

The sha256compression opcode is a clear winner, and this is because it
uses UltraPlonk lookup-gates.
As a result, I have removed the 2 other methods in the stdlib. The
stdlib sha256 is now calling the Noir implementation which is using the
sha256compression opcodes.
The old opcode should be removed in a future PR.

---------

Co-authored-by: kevaundray <kevtheappdev@gmail.com>

noir/acvm-repo/acvm/src/pwg/blackbox/hash.rs

@@ -3,7 +3,7 @@ use acir::{
     native_types::{Witness, WitnessMap},
     BlackBoxFunc, FieldElement,
 };
-use acvm_blackbox_solver::BlackBoxResolutionError;
+use acvm_blackbox_solver::{sha256compression, BlackBoxResolutionError};
 
 use crate::pwg::{insert_value, witness_to_value};
 use crate::OpcodeResolutionError;
@@ -86,3 +86,48 @@ fn write_digest_to_outputs(
 
     Ok(())
 }
+
+pub(crate) fn solve_sha_256_permutation_opcode(
+    initial_witness: &mut WitnessMap,
+    inputs: &[FunctionInput],
+    hash_values: &[FunctionInput],
+    outputs: &[Witness],
+    black_box_func: BlackBoxFunc,
+) -> Result<(), OpcodeResolutionError> {
+    let mut message = [0; 16];
+    if inputs.len() != 16 {
+        return Err(OpcodeResolutionError::BlackBoxFunctionFailed(
+            black_box_func,
+            format!("Expected 16 inputs but encountered {}", &message.len()),
+        ));
+    }
+    for (i, input) in inputs.iter().enumerate() {
+        let value = witness_to_value(initial_witness, input.witness)?;
+        message[i] = value.to_u128() as u32;
+    }
+
+    if hash_values.len() != 8 {
+        return Err(OpcodeResolutionError::BlackBoxFunctionFailed(
+            black_box_func,
+            format!("Expected 8 values but encountered {}", hash_values.len()),
+        ));
+    }
+    let mut state = [0; 8];
+    for (i, hash) in hash_values.iter().enumerate() {
+        let value = witness_to_value(initial_witness, hash.witness)?;
+        state[i] = value.to_u128() as u32;
+    }
+
+    sha256compression(&mut state, &message);
+    let outputs: [Witness; 8] = outputs.try_into().map_err(|_| {
+        OpcodeResolutionError::BlackBoxFunctionFailed(
+            black_box_func,
+            format!("Expected 8 outputs but encountered {}", outputs.len()),
+        )
+    })?;
+    for (output_witness, value) in outputs.iter().zip(state.into_iter()) {
+        insert_value(output_witness, FieldElement::from(value as u128), initial_witness)?;
+    }
+
+    Ok(())
+}

noir/acvm-repo/acvm/src/pwg/blackbox/mod.rs

@@ -20,7 +20,7 @@ mod signature;
 
 use fixed_base_scalar_mul::{embedded_curve_add, fixed_base_scalar_mul};
 // Hash functions should eventually be exposed for external consumers.
-use hash::solve_generic_256_hash_opcode;
+use hash::{solve_generic_256_hash_opcode, solve_sha_256_permutation_opcode};
 use logic::{and, xor};
 use pedersen::pedersen;
 use range::solve_range_opcode;
@@ -205,6 +205,14 @@ pub(crate) fn solve(
             bigint_solver.bigint_to_bytes(*input, outputs, initial_witness)
         }
         BlackBoxFuncCall::Poseidon2Permutation { .. } => todo!(),
-        BlackBoxFuncCall::Sha256Compression { .. } => todo!(),
+        BlackBoxFuncCall::Sha256Compression { inputs, hash_values, outputs } => {
+            solve_sha_256_permutation_opcode(
+                initial_witness,
+                inputs,
+                hash_values,
+                outputs,
+                bb_func.get_black_box_func(),
+            )
+        }
     }
 }

noir/acvm-repo/blackbox_solver/Cargo.toml

@@ -18,7 +18,7 @@ thiserror.workspace = true
 
 blake2 = "0.10.6"
 blake3 = "1.5.0"
-sha2 = "0.10.6"
+sha2 = { version="0.10.6", features = ["compress",] }
 sha3 = "0.10.6"
 keccak = "0.1.4"
 k256 = { version = "0.11.0", features = [

noir/acvm-repo/blackbox_solver/src/lib.rs

@@ -43,6 +43,16 @@ pub fn keccak256(inputs: &[u8]) -> Result<[u8; 32], BlackBoxResolutionError> {
         .map_err(|err| BlackBoxResolutionError::Failed(BlackBoxFunc::Keccak256, err))
 }
 
+pub fn sha256compression(state: &mut [u32; 8], msg_blocks: &[u32; 16]) {
+    let mut blocks = [0_u8; 64];
+    for (i, block) in msg_blocks.iter().enumerate() {
+        let bytes = block.to_be_bytes();
+        blocks[i * 4..i * 4 + 4].copy_from_slice(&bytes);
+    }
+    let blocks: GenericArray<u8, sha2::digest::typenum::U64> = blocks.into();
+    sha2::compress256(state, &[blocks]);
+}
+
 const KECCAK_LANES: usize = 25;
 
 pub fn keccakf1600(

noir/acvm-repo/brillig_vm/src/black_box.rs

@@ -2,7 +2,7 @@ use acir::brillig::{BlackBoxOp, HeapArray, HeapVector, Value};
 use acir::{BlackBoxFunc, FieldElement};
 use acvm_blackbox_solver::{
     blake2s, blake3, ecdsa_secp256k1_verify, ecdsa_secp256r1_verify, keccak256, keccakf1600,
-    sha256, BlackBoxFunctionSolver, BlackBoxResolutionError,
+    sha256, sha256compression, BlackBoxFunctionSolver, BlackBoxResolutionError,
 };
 
 use crate::Memory;
@@ -185,7 +185,36 @@ pub(crate) fn evaluate_black_box<Solver: BlackBoxFunctionSolver>(
         BlackBoxOp::BigIntFromLeBytes { .. } => todo!(),
         BlackBoxOp::BigIntToLeBytes { .. } => todo!(),
         BlackBoxOp::Poseidon2Permutation { .. } => todo!(),
-        BlackBoxOp::Sha256Compression { .. } => todo!(),
+        BlackBoxOp::Sha256Compression { input, hash_values, output } => {
+            let mut message = [0; 16];
+            let inputs = read_heap_vector(memory, input);
+            if inputs.len() != 16 {
+                return Err(BlackBoxResolutionError::Failed(
+                    BlackBoxFunc::Sha256Compression,
+                    format!("Expected 16 inputs but encountered {}", &inputs.len()),
+                ));
+            }
+            for (i, input) in inputs.iter().enumerate() {
+                message[i] = input.to_u128() as u32;
+            }
+            let mut state = [0; 8];
+            let values = read_heap_vector(memory, hash_values);
+            if values.len() != 8 {
+                return Err(BlackBoxResolutionError::Failed(
+                    BlackBoxFunc::Sha256Compression,
+                    format!("Expected 8 values but encountered {}", &values.len()),
+                ));
+            }
+            for (i, value) in values.iter().enumerate() {
+                state[i] = value.to_u128() as u32;
+            }
+
+            sha256compression(&mut state, &message);
+            let state = state.map(|x| Value::from(x as u128));
+
+            memory.write_slice(memory.read_ref(output.pointer), &state);
+            Ok(())
+        }
     }
 }
 

noir/noir_stdlib/src/sha256.nr

@@ -1,91 +1,6 @@
 // Implementation of SHA-256 mapping a byte array of variable length to
 // 32 bytes.
-// Internal functions act on 32-bit unsigned integers for simplicity.
-// Auxiliary mappings; names as in FIPS PUB 180-4
-fn rotr32(a: u32, b: u32) -> u32 // 32-bit right rotation
-{
-    // None of the bits overlap between `(a >> b)` and `(a << (32 - b))`
-    // Addition is then equivalent to OR, with fewer constraints.
-    (a >> b) + (a << (32 - b))
-}
-
-fn ch(x: u32, y: u32, z: u32) -> u32 {
-    (x & y) ^ ((!x) & z)
-}
-
-fn maj(x: u32, y: u32, z: u32) -> u32 {
-    (x & y) ^ (x & z) ^ (y & z)
-}
-
-fn bigma0(x: u32) -> u32 {
-    rotr32(x, 2) ^ rotr32(x, 13) ^ rotr32(x, 22)
-}
 
-fn bigma1(x: u32) -> u32 {
-    rotr32(x, 6) ^ rotr32(x, 11) ^ rotr32(x, 25)
-}
-
-fn sigma0(x: u32) -> u32 {
-    rotr32(x, 7) ^ rotr32(x, 18) ^ (x >> 3)
-}
-
-fn sigma1(x: u32) -> u32 {
-    rotr32(x, 17) ^ rotr32(x, 19) ^ (x >> 10)
-}
-
-fn sha_w(msg: [u32; 16]) -> [u32; 64] // Expanded message blocks
-{
-    let mut w: [u32;64] = [0; 64];
-
-    for j in 0..16 {
-        w[j] = msg[j];
-    }
-
-    for j in 16..64 {
-        w[j] = crate::wrapping_add(
-            crate::wrapping_add(sigma1(w[j-2]), w[j-7]), 
-            crate::wrapping_add(sigma0(w[j-15]), w[j-16]),
-        );
-    }
-
-    w
-}
-// SHA-256 compression function
-fn sha_c(msg: [u32; 16], hash: [u32; 8]) -> [u32; 8] {
-    let K: [u32; 64] = [
-        1116352408, 1899447441, 3049323471, 3921009573, 961987163, 1508970993, 2453635748,
-        2870763221, 3624381080, 310598401, 607225278, 1426881987, 1925078388, 2162078206,
-        2614888103, 3248222580, 3835390401, 4022224774, 264347078, 604807628, 770255983, 1249150122,
-        1555081692, 1996064986, 2554220882, 2821834349, 2952996808, 3210313671, 3336571891,
-        3584528711, 113926993, 338241895, 666307205, 773529912, 1294757372, 1396182291, 1695183700,
-        1986661051, 2177026350, 2456956037, 2730485921, 2820302411, 3259730800, 3345764771,
-        3516065817, 3600352804, 4094571909, 275423344, 430227734, 506948616, 659060556, 883997877,
-        958139571, 1322822218, 1537002063, 1747873779, 1955562222, 2024104815, 2227730452,
-        2361852424, 2428436474, 2756734187, 3204031479, 3329325298
-    ]; // first 32 bits of fractional parts of cube roots of first 64 primes
-    let mut out_h: [u32; 8] = hash;
-    let w = sha_w(msg);
-    for j in 0..64 {
-        let t1 = crate::wrapping_add(
-            crate::wrapping_add(
-                crate::wrapping_add(out_h[7], bigma1(out_h[4])),
-                ch(out_h[4], out_h[5], out_h[6])
-            ),
-            crate::wrapping_add(K[j], w[j])
-        );
-        let t2 = crate::wrapping_add(bigma0(out_h[0]), maj(out_h[0], out_h[1], out_h[2]));
-        out_h[7] = out_h[6];
-        out_h[6] = out_h[5];
-        out_h[5] = out_h[4];
-        out_h[4] = crate::wrapping_add(out_h[3], t1);
-        out_h[3] = out_h[2];
-        out_h[2] = out_h[1];
-        out_h[1] = out_h[0];
-        out_h[0] = crate::wrapping_add(t1, t2);
-    }
-
-    out_h
-}
 // Convert 64-byte array to array of 16 u32s
 fn msg_u8_to_u32(msg: [u8; 64]) -> [u32; 16] {
     let mut msg32: [u32; 16] = [0; 16];
@@ -102,19 +17,15 @@ fn msg_u8_to_u32(msg: [u8; 64]) -> [u32; 16] {
 pub fn digest<N>(msg: [u8; N]) -> [u8; 32] {
     let mut msg_block: [u8; 64] = [0; 64];
     let mut h: [u32; 8] = [1779033703, 3144134277, 1013904242, 2773480762, 1359893119, 2600822924, 528734635, 1541459225]; // Intermediate hash, starting with the canonical initial value
-    let mut c: [u32; 8] = [0; 8]; // Compression of current message block as sequence of u32
     let mut out_h: [u8; 32] = [0; 32]; // Digest as sequence of bytes
     let mut i: u64 = 0; // Message byte pointer
-    for k in 0..msg.len() {
+    for k in 0..N {
         // Populate msg_block
         msg_block[i as Field] = msg[k];
         i = i + 1;
         if i == 64 {
             // Enough to hash block
-            c = sha_c(msg_u8_to_u32(msg_block), h);
-            for j in 0..8 {
-                h[j] = crate::wrapping_add(c[j], h[j]);
-            }
+            h = crate::hash::sha256_compression(msg_u8_to_u32(msg_block), h);
 
             i = 0;
         }
@@ -135,11 +46,7 @@ pub fn digest<N>(msg: [u8; N]) -> [u8; 32] {
                 }
             }
         }
-        c = h;
-        c = sha_c(msg_u8_to_u32(msg_block), c);
-        for j in 0..8 {
-            h[j] = crate::wrapping_add(h[j], c[j]);
-        }
+        h = crate::hash::sha256_compression(msg_u8_to_u32(msg_block), h);
 
         i = 0;
     }
@@ -159,11 +66,8 @@ pub fn digest<N>(msg: [u8; N]) -> [u8; 32] {
         }
     }
     // Hash final padded block
-    c = h;
-    c = sha_c(msg_u8_to_u32(msg_block), c);
-    for j in 0..8 {
-        h[j] = crate::wrapping_add(h[j], c[j]);
-    }
+    h = crate::hash::sha256_compression(msg_u8_to_u32(msg_block), h);
+
     // Return final hash as byte array
     for j in 0..8 {
         for k in 0..4 {