From 1bf4565f1289662c2d2777754315645280da8515 Mon Sep 17 00:00:00 2001
From: KimiWu <leonhartwu@gmail.com>
Date: Thu, 19 Oct 2023 12:13:35 +0800
Subject: [PATCH] feat: impl. ecRecover

---
 specs/precompile/01ecRecover.md               |  2 +-
 .../execution/precompiles/ecrecover.py        | 67 +++++++++++++++++++
 src/zkevm_specs/evm_circuit/step.py           |  2 +-
 3 files changed, 69 insertions(+), 2 deletions(-)

diff --git a/specs/precompile/01ecRecover.md b/specs/precompile/01ecRecover.md
index c4221c1aa..a607f853f 100644
--- a/specs/precompile/01ecRecover.md
+++ b/specs/precompile/01ecRecover.md
@@ -22,7 +22,7 @@ A constant gas cost: 3000
 
 1. If gas_left < gas_required, then is_success == false and return data is zero.
 1. v, r and s are valid
-  - v is 27 or 28 and the first 31 bytes of v is zero
+  - v is 27 or 28
   - both of r and s are less than `secp256k1N (0xfffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141)`
   - both of r and s are greater than `1`
 2. `sig_table` lookups
diff --git a/src/zkevm_specs/evm_circuit/execution/precompiles/ecrecover.py b/src/zkevm_specs/evm_circuit/execution/precompiles/ecrecover.py
index e69de29bb..14220737c 100644
--- a/src/zkevm_specs/evm_circuit/execution/precompiles/ecrecover.py
+++ b/src/zkevm_specs/evm_circuit/execution/precompiles/ecrecover.py
@@ -0,0 +1,67 @@
+from instruction import Instruction, Transition
+from table import (
+    CallContextFieldTag,
+    FixedTableTag,
+    RW,
+)
+from zkevm_specs.util import FQ, Word, EcrecoverGas
+
+SECP256K1N = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141
+
+
+def ecRecover(instruction: Instruction):
+    is_success = instruction.call_context_lookup(CallContextFieldTag.IsSuccess, RW.Read)
+    address_word = instruction.call_context_lookup_word(CallContextFieldTag.CalleeAddress)
+    address = instruction.word_to_address(address_word)
+    instruction.fixed_lookup(
+        FixedTableTag.PrecompileInfo,
+        FQ(instruction.curr.execution_state),
+        address,
+        FQ(EcrecoverGas),
+    )
+
+    # Get msg_hash, signature and recovered address from aux_data
+    msg_hash = instruction.curr.aux_data[0]
+    sig_v = instruction.curr.aux_data[1]
+    sig_r = instruction.curr.aux_data[2]
+    sig_s = instruction.curr.aux_data[3]
+    recovered_addr = instruction.curr.aux_data[4]
+
+    is_recovered = FQ(instruction.is_zero_word(recovered_addr) != FQ(0))
+
+    # if the address is recovered, this call should be success either
+    instruction.constrain_equal(is_success, is_recovered)
+
+    # verify r and s
+    sig_r_upper_bound, _ = instruction.compare_word(sig_r, Word(SECP256K1N))
+    sig_s_upper_bound, _ = instruction.compare_word(sig_s, Word(SECP256K1N))
+    sig_r_lower_bound, _ = instruction.compare_word(Word(1), sig_r)
+    sig_s_lower_bound, _ = instruction.compare_word(Word(1), sig_s)
+    valid_r_s = instruction.is_equal(
+        sig_r_upper_bound + sig_s_upper_bound + sig_r_lower_bound + sig_s_lower_bound, FQ(4)
+    )
+
+    # verify v
+    is_equal_27 = instruction.is_equal_word(sig_v, Word(27))
+    is_equal_28 = instruction.is_equal_word(sig_v, Word(28))
+    valid_v = instruction.is_equal(is_equal_27 + is_equal_28, FQ(1))
+
+    if valid_r_s + valid_v == FQ(2):
+        # sig table lookups
+        instruction.sig_lookup(
+            msg_hash, sig_v - FQ(27).expr(), sig_r, sig_s, recovered_addr, is_recovered
+        )
+    else:
+        instruction.constrain_zero(is_recovered)
+        instruction.constrain_zero(recovered_addr)
+
+    # calculate gas cost
+    gas_cost = EcrecoverGas if is_success == FQ(1) else instruction.curr.gas_left
+
+    # Restore caller state to next StepState
+    instruction.step_state_transition_to_restored_context(
+        rw_counter_delta=instruction.rw_counter_offset,
+        return_data_offset=FQ(0),
+        return_data_length=32 if is_success == FQ(1) else 0,
+        gas_left=Transition.delta(-gas_cost),
+    )
diff --git a/src/zkevm_specs/evm_circuit/step.py b/src/zkevm_specs/evm_circuit/step.py
index 345620d9a..c675f1714 100644
--- a/src/zkevm_specs/evm_circuit/step.py
+++ b/src/zkevm_specs/evm_circuit/step.py
@@ -41,7 +41,7 @@ class StepState:
     # not often used.
     log_id: FQ
 
-    # Auxilary witness data needed by gadgets
+    # Auxiliary witness data needed by gadgets
     aux_data: Any
 
     def __init__(