diff --git a/evm/src/cpu/kernel/interpreter.rs b/evm/src/cpu/kernel/interpreter.rs
index c4deba99..8f19a072 100644
--- a/evm/src/cpu/kernel/interpreter.rs
+++ b/evm/src/cpu/kernel/interpreter.rs
@@ -117,7 +117,7 @@ impl<'a> Interpreter<'a> {
         let mut result = Self {
             kernel_mode: true,
             jumpdests: find_jumpdests(code),
-            generation_state: GenerationState::new(GenerationInputs::default(), code),
+            generation_state: GenerationState::new(GenerationInputs::default(), code).unwrap(),
             prover_inputs_map: prover_inputs,
             context: 0,
             halt_offsets: vec![DEFAULT_HALT_OFFSET],
@@ -905,7 +905,10 @@ impl<'a> Interpreter<'a> {
             .prover_inputs_map
             .get(&(self.generation_state.registers.program_counter - 1))
             .ok_or_else(|| anyhow!("Offset not in prover inputs."))?;
-        let output = self.generation_state.prover_input(prover_input_fn);
+        let output = self
+            .generation_state
+            .prover_input(prover_input_fn)
+            .map_err(|_| anyhow!("Invalid prover inputs."))?;
         self.push(output);
         Ok(())
     }
diff --git a/evm/src/cpu/kernel/tests/account_code.rs b/evm/src/cpu/kernel/tests/account_code.rs
index 805fed04..f4c18fe6 100644
--- a/evm/src/cpu/kernel/tests/account_code.rs
+++ b/evm/src/cpu/kernel/tests/account_code.rs
@@ -1,6 +1,6 @@
 use std::collections::HashMap;
 
-use anyhow::Result;
+use anyhow::{anyhow, Result};
 use eth_trie_utils::partial_trie::{HashedPartialTrie, PartialTrie};
 use ethereum_types::{Address, BigEndianHash, H256, U256};
 use keccak_hash::keccak;
@@ -46,7 +46,9 @@ fn prepare_interpreter(
     interpreter.generation_state.registers.program_counter = load_all_mpts;
     interpreter.push(0xDEADBEEFu32.into());
 
-    interpreter.generation_state.mpt_prover_inputs = all_mpt_prover_inputs_reversed(&trie_inputs);
+    interpreter.generation_state.mpt_prover_inputs =
+        all_mpt_prover_inputs_reversed(&trie_inputs)
+            .map_err(|err| anyhow!("Invalid MPT data: {:?}", err))?;
     interpreter.run()?;
     assert_eq!(interpreter.stack(), vec![]);
 
diff --git a/evm/src/cpu/kernel/tests/balance.rs b/evm/src/cpu/kernel/tests/balance.rs
index 049bf9f8..40214405 100644
--- a/evm/src/cpu/kernel/tests/balance.rs
+++ b/evm/src/cpu/kernel/tests/balance.rs
@@ -1,4 +1,4 @@
-use anyhow::Result;
+use anyhow::{anyhow, Result};
 use eth_trie_utils::partial_trie::{HashedPartialTrie, PartialTrie};
 use ethereum_types::{Address, BigEndianHash, H256, U256};
 use keccak_hash::keccak;
@@ -37,7 +37,9 @@ fn prepare_interpreter(
     interpreter.generation_state.registers.program_counter = load_all_mpts;
     interpreter.push(0xDEADBEEFu32.into());
 
-    interpreter.generation_state.mpt_prover_inputs = all_mpt_prover_inputs_reversed(&trie_inputs);
+    interpreter.generation_state.mpt_prover_inputs =
+        all_mpt_prover_inputs_reversed(&trie_inputs)
+            .map_err(|err| anyhow!("Invalid MPT data: {:?}", err))?;
     interpreter.run()?;
     assert_eq!(interpreter.stack(), vec![]);
 
diff --git a/evm/src/cpu/kernel/tests/mpt/delete.rs b/evm/src/cpu/kernel/tests/mpt/delete.rs
index 532a1603..42e8caf9 100644
--- a/evm/src/cpu/kernel/tests/mpt/delete.rs
+++ b/evm/src/cpu/kernel/tests/mpt/delete.rs
@@ -1,4 +1,4 @@
-use anyhow::Result;
+use anyhow::{anyhow, Result};
 use eth_trie_utils::nibbles::Nibbles;
 use eth_trie_utils::partial_trie::{HashedPartialTrie, PartialTrie};
 use ethereum_types::{BigEndianHash, H256};
@@ -61,7 +61,8 @@ fn test_state_trie(
 
     let initial_stack = vec![0xDEADBEEFu32.into()];
     let mut interpreter = Interpreter::new_with_kernel(load_all_mpts, initial_stack);
-    interpreter.generation_state.mpt_prover_inputs = all_mpt_prover_inputs_reversed(&trie_inputs);
+    interpreter.generation_state.mpt_prover_inputs =
+        all_mpt_prover_inputs_reversed(&trie_inputs).map_err(|_| anyhow!("Invalid MPT data"))?;
     interpreter.run()?;
     assert_eq!(interpreter.stack(), vec![]);
 
diff --git a/evm/src/cpu/kernel/tests/mpt/hash.rs b/evm/src/cpu/kernel/tests/mpt/hash.rs
index 3d6c2a23..05077a94 100644
--- a/evm/src/cpu/kernel/tests/mpt/hash.rs
+++ b/evm/src/cpu/kernel/tests/mpt/hash.rs
@@ -1,4 +1,4 @@
-use anyhow::Result;
+use anyhow::{anyhow, Result};
 use eth_trie_utils::partial_trie::PartialTrie;
 use ethereum_types::{BigEndianHash, H256};
 
@@ -113,7 +113,8 @@ fn test_state_trie(trie_inputs: TrieInputs) -> Result<()> {
 
     let initial_stack = vec![0xDEADBEEFu32.into()];
     let mut interpreter = Interpreter::new_with_kernel(load_all_mpts, initial_stack);
-    interpreter.generation_state.mpt_prover_inputs = all_mpt_prover_inputs_reversed(&trie_inputs);
+    interpreter.generation_state.mpt_prover_inputs =
+        all_mpt_prover_inputs_reversed(&trie_inputs).map_err(|_| anyhow!("Invalid MPT data"))?;
     interpreter.run()?;
     assert_eq!(interpreter.stack(), vec![]);
 
diff --git a/evm/src/cpu/kernel/tests/mpt/insert.rs b/evm/src/cpu/kernel/tests/mpt/insert.rs
index f8dbc274..6fd95a30 100644
--- a/evm/src/cpu/kernel/tests/mpt/insert.rs
+++ b/evm/src/cpu/kernel/tests/mpt/insert.rs
@@ -1,4 +1,4 @@
-use anyhow::Result;
+use anyhow::{anyhow, Result};
 use eth_trie_utils::nibbles::Nibbles;
 use eth_trie_utils::partial_trie::{HashedPartialTrie, PartialTrie};
 use ethereum_types::{BigEndianHash, H256};
@@ -174,7 +174,8 @@ fn test_state_trie(
 
     let initial_stack = vec![0xDEADBEEFu32.into()];
     let mut interpreter = Interpreter::new_with_kernel(load_all_mpts, initial_stack);
-    interpreter.generation_state.mpt_prover_inputs = all_mpt_prover_inputs_reversed(&trie_inputs);
+    interpreter.generation_state.mpt_prover_inputs =
+        all_mpt_prover_inputs_reversed(&trie_inputs).map_err(|_| anyhow!("Invalid MPT data"))?;
     interpreter.run()?;
     assert_eq!(interpreter.stack(), vec![]);
 
diff --git a/evm/src/cpu/kernel/tests/mpt/load.rs b/evm/src/cpu/kernel/tests/mpt/load.rs
index aed311d2..50a8a0ef 100644
--- a/evm/src/cpu/kernel/tests/mpt/load.rs
+++ b/evm/src/cpu/kernel/tests/mpt/load.rs
@@ -1,4 +1,4 @@
-use anyhow::Result;
+use anyhow::{anyhow, Result};
 use ethereum_types::{BigEndianHash, H256, U256};
 
 use crate::cpu::kernel::aggregator::KERNEL;
@@ -23,7 +23,9 @@ fn load_all_mpts_empty() -> Result<()> {
 
     let initial_stack = vec![0xDEADBEEFu32.into()];
     let mut interpreter = Interpreter::new_with_kernel(load_all_mpts, initial_stack);
-    interpreter.generation_state.mpt_prover_inputs = all_mpt_prover_inputs_reversed(&trie_inputs);
+    interpreter.generation_state.mpt_prover_inputs =
+        all_mpt_prover_inputs_reversed(&trie_inputs)
+            .map_err(|err| anyhow!("Invalid MPT data: {:?}", err))?;
     interpreter.run()?;
     assert_eq!(interpreter.stack(), vec![]);
 
@@ -62,7 +64,9 @@ fn load_all_mpts_leaf() -> Result<()> {
 
     let initial_stack = vec![0xDEADBEEFu32.into()];
     let mut interpreter = Interpreter::new_with_kernel(load_all_mpts, initial_stack);
-    interpreter.generation_state.mpt_prover_inputs = all_mpt_prover_inputs_reversed(&trie_inputs);
+    interpreter.generation_state.mpt_prover_inputs =
+        all_mpt_prover_inputs_reversed(&trie_inputs)
+            .map_err(|err| anyhow!("Invalid MPT data: {:?}", err))?;
     interpreter.run()?;
     assert_eq!(interpreter.stack(), vec![]);
 
@@ -111,7 +115,9 @@ fn load_all_mpts_hash() -> Result<()> {
 
     let initial_stack = vec![0xDEADBEEFu32.into()];
     let mut interpreter = Interpreter::new_with_kernel(load_all_mpts, initial_stack);
-    interpreter.generation_state.mpt_prover_inputs = all_mpt_prover_inputs_reversed(&trie_inputs);
+    interpreter.generation_state.mpt_prover_inputs =
+        all_mpt_prover_inputs_reversed(&trie_inputs)
+            .map_err(|err| anyhow!("Invalid MPT data: {:?}", err))?;
     interpreter.run()?;
     assert_eq!(interpreter.stack(), vec![]);
 
@@ -152,7 +158,9 @@ fn load_all_mpts_empty_branch() -> Result<()> {
 
     let initial_stack = vec![0xDEADBEEFu32.into()];
     let mut interpreter = Interpreter::new_with_kernel(load_all_mpts, initial_stack);
-    interpreter.generation_state.mpt_prover_inputs = all_mpt_prover_inputs_reversed(&trie_inputs);
+    interpreter.generation_state.mpt_prover_inputs =
+        all_mpt_prover_inputs_reversed(&trie_inputs)
+            .map_err(|err| anyhow!("Invalid MPT data: {:?}", err))?;
     interpreter.run()?;
     assert_eq!(interpreter.stack(), vec![]);
 
@@ -207,7 +215,9 @@ fn load_all_mpts_ext_to_leaf() -> Result<()> {
 
     let initial_stack = vec![0xDEADBEEFu32.into()];
     let mut interpreter = Interpreter::new_with_kernel(load_all_mpts, initial_stack);
-    interpreter.generation_state.mpt_prover_inputs = all_mpt_prover_inputs_reversed(&trie_inputs);
+    interpreter.generation_state.mpt_prover_inputs =
+        all_mpt_prover_inputs_reversed(&trie_inputs)
+            .map_err(|err| anyhow!("Invalid MPT data: {:?}", err))?;
     interpreter.run()?;
     assert_eq!(interpreter.stack(), vec![]);
 
diff --git a/evm/src/cpu/kernel/tests/mpt/read.rs b/evm/src/cpu/kernel/tests/mpt/read.rs
index 62313f62..f9ae94f0 100644
--- a/evm/src/cpu/kernel/tests/mpt/read.rs
+++ b/evm/src/cpu/kernel/tests/mpt/read.rs
@@ -1,4 +1,4 @@
-use anyhow::Result;
+use anyhow::{anyhow, Result};
 use ethereum_types::BigEndianHash;
 
 use crate::cpu::kernel::aggregator::KERNEL;
@@ -22,7 +22,9 @@ fn mpt_read() -> Result<()> {
 
     let initial_stack = vec![0xdeadbeefu32.into()];
     let mut interpreter = Interpreter::new_with_kernel(load_all_mpts, initial_stack);
-    interpreter.generation_state.mpt_prover_inputs = all_mpt_prover_inputs_reversed(&trie_inputs);
+    interpreter.generation_state.mpt_prover_inputs =
+        all_mpt_prover_inputs_reversed(&trie_inputs)
+            .map_err(|err| anyhow!("Invalid MPT data: {:?}", err))?;
     interpreter.run()?;
     assert_eq!(interpreter.stack(), vec![]);
 
diff --git a/evm/src/cpu/kernel/tests/receipt.rs b/evm/src/cpu/kernel/tests/receipt.rs
index 783f592b..b5583654 100644
--- a/evm/src/cpu/kernel/tests/receipt.rs
+++ b/evm/src/cpu/kernel/tests/receipt.rs
@@ -1,4 +1,4 @@
-use anyhow::Result;
+use anyhow::{anyhow, Result};
 use ethereum_types::{Address, U256};
 use hex_literal::hex;
 use keccak_hash::keccak;
@@ -413,7 +413,9 @@ fn test_mpt_insert_receipt() -> Result<()> {
     let initial_stack = vec![retdest];
 
     let mut interpreter = Interpreter::new_with_kernel(load_all_mpts, initial_stack);
-    interpreter.generation_state.mpt_prover_inputs = all_mpt_prover_inputs_reversed(&trie_inputs);
+    interpreter.generation_state.mpt_prover_inputs =
+        all_mpt_prover_inputs_reversed(&trie_inputs)
+            .map_err(|err| anyhow!("Invalid MPT data: {:?}", err))?;
     interpreter.run()?;
 
     // If TrieData is empty, we need to push 0 because the first value is always 0.
diff --git a/evm/src/generation/mod.rs b/evm/src/generation/mod.rs
index 3f5bafba..6b9ce000 100644
--- a/evm/src/generation/mod.rs
+++ b/evm/src/generation/mod.rs
@@ -1,5 +1,6 @@
 use std::collections::HashMap;
 
+use anyhow::anyhow;
 use eth_trie_utils::partial_trie::{HashedPartialTrie, PartialTrie};
 use ethereum_types::{Address, BigEndianHash, H256, U256};
 use plonky2::field::extension::Extendable;
@@ -220,7 +221,8 @@ pub fn generate_traces<F: RichField + Extendable<D>, const D: usize>(
     PublicValues,
     GenerationOutputs,
 )> {
-    let mut state = GenerationState::<F>::new(inputs.clone(), &KERNEL.code);
+    let mut state = GenerationState::<F>::new(inputs.clone(), &KERNEL.code)
+        .map_err(|err| anyhow!("Failed to parse all the initial prover inputs: {:?}", err))?;
 
     apply_metadata_and_tries_memops(&mut state, &inputs);
 
@@ -238,7 +240,8 @@ pub fn generate_traces<F: RichField + Extendable<D>, const D: usize>(
         state.traces.get_lengths()
     );
 
-    let outputs = get_outputs(&mut state);
+    let outputs = get_outputs(&mut state)
+        .map_err(|err| anyhow!("Failed to generate post-state info: {:?}", err))?;
 
     let read_metadata = |field| state.memory.read_global_metadata(field);
     let trie_roots_before = TrieRoots {
diff --git a/evm/src/generation/mpt.rs b/evm/src/generation/mpt.rs
index 47129ed0..dbc36cac 100644
--- a/evm/src/generation/mpt.rs
+++ b/evm/src/generation/mpt.rs
@@ -11,6 +11,7 @@ use rlp_derive::{RlpDecodable, RlpEncodable};
 
 use crate::cpu::kernel::constants::trie_type::PartialTrieType;
 use crate::generation::TrieInputs;
+use crate::witness::errors::{ProgramError, ProverInputError};
 use crate::Node;
 
 #[derive(RlpEncodable, RlpDecodable, Debug)]
@@ -60,15 +61,18 @@ pub struct LegacyReceiptRlp {
     pub logs: Vec<LogRlp>,
 }
 
-pub(crate) fn all_mpt_prover_inputs_reversed(trie_inputs: &TrieInputs) -> Vec<U256> {
-    let mut inputs = all_mpt_prover_inputs(trie_inputs);
+pub(crate) fn all_mpt_prover_inputs_reversed(
+    trie_inputs: &TrieInputs,
+) -> Result<Vec<U256>, ProgramError> {
+    let mut inputs = all_mpt_prover_inputs(trie_inputs)?;
     inputs.reverse();
-    inputs
+    Ok(inputs)
 }
 
-pub(crate) fn parse_receipts(rlp: &[u8]) -> Vec<U256> {
-    let payload_info = PayloadInfo::from(rlp).unwrap();
-    let decoded_receipt: LegacyReceiptRlp = rlp::decode(rlp).unwrap();
+pub(crate) fn parse_receipts(rlp: &[u8]) -> Result<Vec<U256>, ProgramError> {
+    let payload_info = PayloadInfo::from(rlp).map_err(|_| ProgramError::InvalidRlp)?;
+    let decoded_receipt: LegacyReceiptRlp =
+        rlp::decode(rlp).map_err(|_| ProgramError::InvalidRlp)?;
     let mut parsed_receipt = Vec::new();
 
     parsed_receipt.push(payload_info.value_len.into()); // payload_len of the entire receipt
@@ -76,13 +80,15 @@ pub(crate) fn parse_receipts(rlp: &[u8]) -> Vec<U256> {
     parsed_receipt.push(decoded_receipt.cum_gas_used);
     parsed_receipt.extend(decoded_receipt.bloom.iter().map(|byte| U256::from(*byte)));
     let encoded_logs = rlp::encode_list(&decoded_receipt.logs);
-    let logs_payload_info = PayloadInfo::from(&encoded_logs).unwrap();
+    let logs_payload_info =
+        PayloadInfo::from(&encoded_logs).map_err(|_| ProgramError::InvalidRlp)?;
     parsed_receipt.push(logs_payload_info.value_len.into()); // payload_len of all the logs
     parsed_receipt.push(decoded_receipt.logs.len().into());
 
     for log in decoded_receipt.logs {
         let encoded_log = rlp::encode(&log);
-        let log_payload_info = PayloadInfo::from(&encoded_log).unwrap();
+        let log_payload_info =
+            PayloadInfo::from(&encoded_log).map_err(|_| ProgramError::InvalidRlp)?;
         parsed_receipt.push(log_payload_info.value_len.into()); // payload of one log
         parsed_receipt.push(U256::from_big_endian(&log.address.to_fixed_bytes()));
         parsed_receipt.push(log.topics.len().into());
@@ -91,10 +97,10 @@ pub(crate) fn parse_receipts(rlp: &[u8]) -> Vec<U256> {
         parsed_receipt.extend(log.data.iter().map(|byte| U256::from(*byte)));
     }
 
-    parsed_receipt
+    Ok(parsed_receipt)
 }
 /// Generate prover inputs for the initial MPT data, in the format expected by `mpt/load.asm`.
-pub(crate) fn all_mpt_prover_inputs(trie_inputs: &TrieInputs) -> Vec<U256> {
+pub(crate) fn all_mpt_prover_inputs(trie_inputs: &TrieInputs) -> Result<Vec<U256>, ProgramError> {
     let mut prover_inputs = vec![];
 
     let storage_tries_by_state_key = trie_inputs
@@ -111,19 +117,19 @@ pub(crate) fn all_mpt_prover_inputs(trie_inputs: &TrieInputs) -> Vec<U256> {
         empty_nibbles(),
         &mut prover_inputs,
         &storage_tries_by_state_key,
-    );
+    )?;
 
     mpt_prover_inputs(&trie_inputs.transactions_trie, &mut prover_inputs, &|rlp| {
-        rlp::decode_list(rlp)
-    });
+        Ok(rlp::decode_list(rlp))
+    })?;
 
     mpt_prover_inputs(
         &trie_inputs.receipts_trie,
         &mut prover_inputs,
         &parse_receipts,
-    );
+    )?;
 
-    prover_inputs
+    Ok(prover_inputs)
 }
 
 /// Given a trie, generate the prover input data for that trie. In essence, this serializes a trie
@@ -134,36 +140,52 @@ pub(crate) fn mpt_prover_inputs<F>(
     trie: &HashedPartialTrie,
     prover_inputs: &mut Vec<U256>,
     parse_value: &F,
-) where
-    F: Fn(&[u8]) -> Vec<U256>,
+) -> Result<(), ProgramError>
+where
+    F: Fn(&[u8]) -> Result<Vec<U256>, ProgramError>,
 {
     prover_inputs.push((PartialTrieType::of(trie) as u32).into());
 
     match trie.deref() {
-        Node::Empty => {}
-        Node::Hash(h) => prover_inputs.push(U256::from_big_endian(h.as_bytes())),
+        Node::Empty => Ok(()),
+        Node::Hash(h) => {
+            prover_inputs.push(U256::from_big_endian(h.as_bytes()));
+            Ok(())
+        }
         Node::Branch { children, value } => {
             if value.is_empty() {
                 prover_inputs.push(U256::zero()); // value_present = 0
             } else {
-                let parsed_value = parse_value(value);
+                let parsed_value = parse_value(value)?;
                 prover_inputs.push(U256::one()); // value_present = 1
                 prover_inputs.extend(parsed_value);
             }
             for child in children {
-                mpt_prover_inputs(child, prover_inputs, parse_value);
+                mpt_prover_inputs(child, prover_inputs, parse_value)?;
             }
+
+            Ok(())
         }
         Node::Extension { nibbles, child } => {
             prover_inputs.push(nibbles.count.into());
-            prover_inputs.push(nibbles.try_into_u256().unwrap());
-            mpt_prover_inputs(child, prover_inputs, parse_value);
+            prover_inputs.push(
+                nibbles
+                    .try_into_u256()
+                    .map_err(|_| ProgramError::IntegerTooLarge)?,
+            );
+            mpt_prover_inputs(child, prover_inputs, parse_value)
         }
         Node::Leaf { nibbles, value } => {
             prover_inputs.push(nibbles.count.into());
-            prover_inputs.push(nibbles.try_into_u256().unwrap());
-            let leaf = parse_value(value);
+            prover_inputs.push(
+                nibbles
+                    .try_into_u256()
+                    .map_err(|_| ProgramError::IntegerTooLarge)?,
+            );
+            let leaf = parse_value(value)?;
             prover_inputs.extend(leaf);
+
+            Ok(())
         }
     }
 }
@@ -175,13 +197,20 @@ pub(crate) fn mpt_prover_inputs_state_trie(
     key: Nibbles,
     prover_inputs: &mut Vec<U256>,
     storage_tries_by_state_key: &HashMap<Nibbles, &HashedPartialTrie>,
-) {
+) -> Result<(), ProgramError> {
     prover_inputs.push((PartialTrieType::of(trie) as u32).into());
     match trie.deref() {
-        Node::Empty => {}
-        Node::Hash(h) => prover_inputs.push(U256::from_big_endian(h.as_bytes())),
+        Node::Empty => Ok(()),
+        Node::Hash(h) => {
+            prover_inputs.push(U256::from_big_endian(h.as_bytes()));
+            Ok(())
+        }
         Node::Branch { children, value } => {
-            assert!(value.is_empty(), "State trie should not have branch values");
+            if !value.is_empty() {
+                return Err(ProgramError::ProverInputError(
+                    ProverInputError::InvalidMptInput,
+                ));
+            }
             prover_inputs.push(U256::zero()); // value_present = 0
 
             for (i, child) in children.iter().enumerate() {
@@ -194,22 +223,28 @@ pub(crate) fn mpt_prover_inputs_state_trie(
                     extended_key,
                     prover_inputs,
                     storage_tries_by_state_key,
-                );
+                )?;
             }
+
+            Ok(())
         }
         Node::Extension { nibbles, child } => {
             prover_inputs.push(nibbles.count.into());
-            prover_inputs.push(nibbles.try_into_u256().unwrap());
+            prover_inputs.push(
+                nibbles
+                    .try_into_u256()
+                    .map_err(|_| ProgramError::IntegerTooLarge)?,
+            );
             let extended_key = key.merge_nibbles(nibbles);
             mpt_prover_inputs_state_trie(
                 child,
                 extended_key,
                 prover_inputs,
                 storage_tries_by_state_key,
-            );
+            )
         }
         Node::Leaf { nibbles, value } => {
-            let account: AccountRlp = rlp::decode(value).expect("Decoding failed");
+            let account: AccountRlp = rlp::decode(value).map_err(|_| ProgramError::InvalidRlp)?;
             let AccountRlp {
                 nonce,
                 balance,
@@ -228,18 +263,24 @@ pub(crate) fn mpt_prover_inputs_state_trie(
                        "In TrieInputs, an account's storage_root didn't match the associated storage trie hash");
 
             prover_inputs.push(nibbles.count.into());
-            prover_inputs.push(nibbles.try_into_u256().unwrap());
+            prover_inputs.push(
+                nibbles
+                    .try_into_u256()
+                    .map_err(|_| ProgramError::IntegerTooLarge)?,
+            );
             prover_inputs.push(nonce);
             prover_inputs.push(balance);
-            mpt_prover_inputs(storage_trie, prover_inputs, &parse_storage_value);
+            mpt_prover_inputs(storage_trie, prover_inputs, &parse_storage_value)?;
             prover_inputs.push(code_hash.into_uint());
+
+            Ok(())
         }
     }
 }
 
-fn parse_storage_value(value_rlp: &[u8]) -> Vec<U256> {
-    let value: U256 = rlp::decode(value_rlp).expect("Decoding failed");
-    vec![value]
+fn parse_storage_value(value_rlp: &[u8]) -> Result<Vec<U256>, ProgramError> {
+    let value: U256 = rlp::decode(value_rlp).map_err(|_| ProgramError::InvalidRlp)?;
+    Ok(vec![value])
 }
 
 fn empty_nibbles() -> Nibbles {
diff --git a/evm/src/generation/outputs.rs b/evm/src/generation/outputs.rs
index 63a86906..0ce87082 100644
--- a/evm/src/generation/outputs.rs
+++ b/evm/src/generation/outputs.rs
@@ -8,6 +8,8 @@ use crate::generation::state::GenerationState;
 use crate::generation::trie_extractor::{
     read_state_trie_value, read_storage_trie_value, read_trie, AccountTrieRecord,
 };
+use crate::util::u256_to_usize;
+use crate::witness::errors::ProgramError;
 
 /// The post-state after trace generation; intended for debugging.
 #[derive(Clone, Debug)]
@@ -29,47 +31,44 @@ pub struct AccountOutput {
     pub storage: HashMap<U256, U256>,
 }
 
-pub(crate) fn get_outputs<F: Field>(state: &mut GenerationState<F>) -> GenerationOutputs {
-    // First observe all addresses passed in the by caller.
+pub(crate) fn get_outputs<F: Field>(
+    state: &mut GenerationState<F>,
+) -> Result<GenerationOutputs, ProgramError> {
+    // First observe all addresses passed in by caller.
     for address in state.inputs.addresses.clone() {
         state.observe_address(address);
     }
 
-    let account_map = read_trie::<AccountTrieRecord>(
-        &state.memory,
-        state.memory.read_global_metadata(StateTrieRoot).as_usize(),
-        read_state_trie_value,
-    );
+    let ptr = u256_to_usize(state.memory.read_global_metadata(StateTrieRoot))?;
+    let account_map = read_trie::<AccountTrieRecord>(&state.memory, ptr, read_state_trie_value)?;
 
-    let accounts = account_map
-        .into_iter()
-        .map(|(state_key_nibbles, account)| {
-            assert_eq!(
-                state_key_nibbles.count, 64,
-                "Each state key should have 64 nibbles = 256 bits"
-            );
-            let state_key_h256 = H256::from_uint(&state_key_nibbles.try_into_u256().unwrap());
+    let mut accounts = HashMap::with_capacity(account_map.len());
 
-            let addr_or_state_key =
-                if let Some(address) = state.state_key_to_address.get(&state_key_h256) {
-                    AddressOrStateKey::Address(*address)
-                } else {
-                    AddressOrStateKey::StateKey(state_key_h256)
-                };
+    for (state_key_nibbles, account) in account_map.into_iter() {
+        if state_key_nibbles.count != 64 {
+            return Err(ProgramError::IntegerTooLarge);
+        }
+        let state_key_h256 = H256::from_uint(&state_key_nibbles.try_into_u256().unwrap());
 
-            let account_output = account_trie_record_to_output(state, account);
-            (addr_or_state_key, account_output)
-        })
-        .collect();
+        let addr_or_state_key =
+            if let Some(address) = state.state_key_to_address.get(&state_key_h256) {
+                AddressOrStateKey::Address(*address)
+            } else {
+                AddressOrStateKey::StateKey(state_key_h256)
+            };
 
-    GenerationOutputs { accounts }
+        let account_output = account_trie_record_to_output(state, account)?;
+        accounts.insert(addr_or_state_key, account_output);
+    }
+
+    Ok(GenerationOutputs { accounts })
 }
 
 fn account_trie_record_to_output<F: Field>(
     state: &GenerationState<F>,
     account: AccountTrieRecord,
-) -> AccountOutput {
-    let storage = get_storage(state, account.storage_ptr);
+) -> Result<AccountOutput, ProgramError> {
+    let storage = get_storage(state, account.storage_ptr)?;
 
     // TODO: This won't work if the account was created during the txn.
     // Need to track changes to code, similar to how we track addresses
@@ -78,27 +77,33 @@ fn account_trie_record_to_output<F: Field>(
         .inputs
         .contract_code
         .get(&account.code_hash)
-        .unwrap_or_else(|| panic!("Code not found: {:?}", account.code_hash))
+        .ok_or(ProgramError::UnknownContractCode)?
         .clone();
 
-    AccountOutput {
+    Ok(AccountOutput {
         balance: account.balance,
         nonce: account.nonce,
         storage,
         code,
-    }
+    })
 }
 
 /// Get an account's storage trie, given a pointer to its root.
-fn get_storage<F: Field>(state: &GenerationState<F>, storage_ptr: usize) -> HashMap<U256, U256> {
-    read_trie::<U256>(&state.memory, storage_ptr, read_storage_trie_value)
-        .into_iter()
-        .map(|(storage_key_nibbles, value)| {
-            assert_eq!(
-                storage_key_nibbles.count, 64,
-                "Each storage key should have 64 nibbles = 256 bits"
-            );
-            (storage_key_nibbles.try_into_u256().unwrap(), value)
-        })
-        .collect()
+fn get_storage<F: Field>(
+    state: &GenerationState<F>,
+    storage_ptr: usize,
+) -> Result<HashMap<U256, U256>, ProgramError> {
+    let storage_trie = read_trie::<U256>(&state.memory, storage_ptr, |x| {
+        Ok(read_storage_trie_value(x))
+    })?;
+
+    let mut map = HashMap::with_capacity(storage_trie.len());
+    for (storage_key_nibbles, value) in storage_trie.into_iter() {
+        if storage_key_nibbles.count != 64 {
+            return Err(ProgramError::IntegerTooLarge);
+        };
+        map.insert(storage_key_nibbles.try_into_u256().unwrap(), value);
+    }
+
+    Ok(map)
 }
diff --git a/evm/src/generation/prover_input.rs b/evm/src/generation/prover_input.rs
index 14293289..205dff7c 100644
--- a/evm/src/generation/prover_input.rs
+++ b/evm/src/generation/prover_input.rs
@@ -16,7 +16,9 @@ use crate::generation::prover_input::FieldOp::{Inverse, Sqrt};
 use crate::generation::state::GenerationState;
 use crate::memory::segments::Segment;
 use crate::memory::segments::Segment::BnPairing;
-use crate::util::{biguint_to_mem_vec, mem_vec_to_biguint};
+use crate::util::{biguint_to_mem_vec, mem_vec_to_biguint, u256_to_usize};
+use crate::witness::errors::ProgramError;
+use crate::witness::errors::ProverInputError::*;
 use crate::witness::util::{current_context_peek, stack_peek};
 
 /// Prover input function represented as a scoped function name.
@@ -31,7 +33,7 @@ impl From<Vec<String>> for ProverInputFn {
 }
 
 impl<F: Field> GenerationState<F> {
-    pub(crate) fn prover_input(&mut self, input_fn: &ProverInputFn) -> U256 {
+    pub(crate) fn prover_input(&mut self, input_fn: &ProverInputFn) -> Result<U256, ProgramError> {
         match input_fn.0[0].as_str() {
             "end_of_txns" => self.run_end_of_txns(),
             "ff" => self.run_ff(input_fn),
@@ -42,51 +44,59 @@ impl<F: Field> GenerationState<F> {
             "current_hash" => self.run_current_hash(),
             "account_code" => self.run_account_code(input_fn),
             "bignum_modmul" => self.run_bignum_modmul(),
-            _ => panic!("Unrecognized prover input function."),
+            _ => Err(ProgramError::ProverInputError(InvalidFunction)),
         }
     }
 
-    fn run_end_of_txns(&mut self) -> U256 {
+    fn run_end_of_txns(&mut self) -> Result<U256, ProgramError> {
         let end = self.next_txn_index == self.inputs.signed_txns.len();
         if end {
-            U256::one()
+            Ok(U256::one())
         } else {
             self.next_txn_index += 1;
-            U256::zero()
+            Ok(U256::zero())
         }
     }
 
     /// Finite field operations.
-    fn run_ff(&self, input_fn: &ProverInputFn) -> U256 {
-        let field = EvmField::from_str(input_fn.0[1].as_str()).unwrap();
-        let op = FieldOp::from_str(input_fn.0[2].as_str()).unwrap();
-        let x = stack_peek(self, 0).expect("Empty stack");
+    fn run_ff(&self, input_fn: &ProverInputFn) -> Result<U256, ProgramError> {
+        let field = EvmField::from_str(input_fn.0[1].as_str())
+            .map_err(|_| ProgramError::ProverInputError(InvalidFunction))?;
+        let op = FieldOp::from_str(input_fn.0[2].as_str())
+            .map_err(|_| ProgramError::ProverInputError(InvalidFunction))?;
+        let x = stack_peek(self, 0)?;
         field.op(op, x)
     }
 
     /// Special finite field operations.
-    fn run_sf(&self, input_fn: &ProverInputFn) -> U256 {
-        let field = EvmField::from_str(input_fn.0[1].as_str()).unwrap();
+    fn run_sf(&self, input_fn: &ProverInputFn) -> Result<U256, ProgramError> {
+        let field = EvmField::from_str(input_fn.0[1].as_str())
+            .map_err(|_| ProgramError::ProverInputError(InvalidFunction))?;
         let inputs: [U256; 4] = match field {
-            Bls381Base => std::array::from_fn(|i| {
-                stack_peek(self, i).expect("Insufficient number of items on stack")
-            }),
+            Bls381Base => (0..4)
+                .map(|i| stack_peek(self, i))
+                .collect::<Result<Vec<U256>, _>>()?
+                .try_into()
+                .unwrap(),
             _ => todo!(),
         };
-        match input_fn.0[2].as_str() {
+        let res = match input_fn.0[2].as_str() {
             "add_lo" => field.add_lo(inputs),
             "add_hi" => field.add_hi(inputs),
             "mul_lo" => field.mul_lo(inputs),
             "mul_hi" => field.mul_hi(inputs),
             "sub_lo" => field.sub_lo(inputs),
             "sub_hi" => field.sub_hi(inputs),
-            _ => todo!(),
-        }
+            _ => return Err(ProgramError::ProverInputError(InvalidFunction)),
+        };
+
+        Ok(res)
     }
 
     /// Finite field extension operations.
-    fn run_ffe(&self, input_fn: &ProverInputFn) -> U256 {
-        let field = EvmField::from_str(input_fn.0[1].as_str()).unwrap();
+    fn run_ffe(&self, input_fn: &ProverInputFn) -> Result<U256, ProgramError> {
+        let field = EvmField::from_str(input_fn.0[1].as_str())
+            .map_err(|_| ProgramError::ProverInputError(InvalidFunction))?;
         let n = input_fn.0[2]
             .as_str()
             .split('_')
@@ -94,61 +104,61 @@ impl<F: Field> GenerationState<F> {
             .unwrap()
             .parse::<usize>()
             .unwrap();
-        let ptr = stack_peek(self, 11 - n)
-            .expect("Insufficient number of items on stack")
-            .as_usize();
+        let ptr = stack_peek(self, 11 - n).map(u256_to_usize)??;
 
         let f: [U256; 12] = match field {
             Bn254Base => std::array::from_fn(|i| current_context_peek(self, BnPairing, ptr + i)),
             _ => todo!(),
         };
-        field.field_extension_inverse(n, f)
+        Ok(field.field_extension_inverse(n, f))
     }
 
     /// MPT data.
-    fn run_mpt(&mut self) -> U256 {
+    fn run_mpt(&mut self) -> Result<U256, ProgramError> {
         self.mpt_prover_inputs
             .pop()
-            .unwrap_or_else(|| panic!("Out of MPT data"))
+            .ok_or(ProgramError::ProverInputError(OutOfMptData))
     }
 
     /// RLP data.
-    fn run_rlp(&mut self) -> U256 {
+    fn run_rlp(&mut self) -> Result<U256, ProgramError> {
         self.rlp_prover_inputs
             .pop()
-            .unwrap_or_else(|| panic!("Out of RLP data"))
+            .ok_or(ProgramError::ProverInputError(OutOfRlpData))
     }
 
-    fn run_current_hash(&mut self) -> U256 {
-        U256::from_big_endian(&self.inputs.block_hashes.cur_hash.0)
+    fn run_current_hash(&mut self) -> Result<U256, ProgramError> {
+        Ok(U256::from_big_endian(&self.inputs.block_hashes.cur_hash.0))
     }
 
     /// Account code.
-    fn run_account_code(&mut self, input_fn: &ProverInputFn) -> U256 {
+    fn run_account_code(&mut self, input_fn: &ProverInputFn) -> Result<U256, ProgramError> {
         match input_fn.0[1].as_str() {
             "length" => {
                 // Return length of code.
                 // stack: codehash, ...
-                let codehash = stack_peek(self, 0).expect("Empty stack");
-                self.inputs
+                let codehash = stack_peek(self, 0)?;
+                Ok(self
+                    .inputs
                     .contract_code
                     .get(&H256::from_uint(&codehash))
-                    .unwrap_or_else(|| panic!("No code found with hash {codehash}"))
+                    .ok_or(ProgramError::ProverInputError(CodeHashNotFound))?
                     .len()
-                    .into()
+                    .into())
             }
             "get" => {
                 // Return `code[i]`.
                 // stack: i, code_length, codehash, ...
-                let i = stack_peek(self, 0).expect("Unexpected stack").as_usize();
-                let codehash = stack_peek(self, 2).expect("Unexpected stack");
-                self.inputs
+                let i = stack_peek(self, 0).map(u256_to_usize)??;
+                let codehash = stack_peek(self, 2)?;
+                Ok(self
+                    .inputs
                     .contract_code
                     .get(&H256::from_uint(&codehash))
-                    .unwrap_or_else(|| panic!("No code found with hash {codehash}"))[i]
-                    .into()
+                    .ok_or(ProgramError::ProverInputError(CodeHashNotFound))?[i]
+                    .into())
             }
-            _ => panic!("Invalid prover input function."),
+            _ => Err(ProgramError::ProverInputError(InvalidInput)),
         }
     }
 
@@ -156,24 +166,12 @@ impl<F: Field> GenerationState<F> {
     // On the first call, calculates the remainder and quotient of the given inputs.
     // These are stored, as limbs, in self.bignum_modmul_result_limbs.
     // Subsequent calls return one limb at a time, in order (first remainder and then quotient).
-    fn run_bignum_modmul(&mut self) -> U256 {
+    fn run_bignum_modmul(&mut self) -> Result<U256, ProgramError> {
         if self.bignum_modmul_result_limbs.is_empty() {
-            let len = stack_peek(self, 1)
-                .expect("Stack does not have enough items")
-                .try_into()
-                .unwrap();
-            let a_start_loc = stack_peek(self, 2)
-                .expect("Stack does not have enough items")
-                .try_into()
-                .unwrap();
-            let b_start_loc = stack_peek(self, 3)
-                .expect("Stack does not have enough items")
-                .try_into()
-                .unwrap();
-            let m_start_loc = stack_peek(self, 4)
-                .expect("Stack does not have enough items")
-                .try_into()
-                .unwrap();
+            let len = stack_peek(self, 1).map(u256_to_usize)??;
+            let a_start_loc = stack_peek(self, 2).map(u256_to_usize)??;
+            let b_start_loc = stack_peek(self, 3).map(u256_to_usize)??;
+            let m_start_loc = stack_peek(self, 4).map(u256_to_usize)??;
 
             let (remainder, quotient) =
                 self.bignum_modmul(len, a_start_loc, b_start_loc, m_start_loc);
@@ -187,7 +185,9 @@ impl<F: Field> GenerationState<F> {
             self.bignum_modmul_result_limbs.reverse();
         }
 
-        self.bignum_modmul_result_limbs.pop().unwrap()
+        self.bignum_modmul_result_limbs
+            .pop()
+            .ok_or(ProgramError::ProverInputError(InvalidInput))
     }
 
     fn bignum_modmul(
@@ -284,27 +284,33 @@ impl EvmField {
         }
     }
 
-    fn op(&self, op: FieldOp, x: U256) -> U256 {
+    fn op(&self, op: FieldOp, x: U256) -> Result<U256, ProgramError> {
         match op {
             FieldOp::Inverse => self.inverse(x),
             FieldOp::Sqrt => self.sqrt(x),
         }
     }
 
-    fn inverse(&self, x: U256) -> U256 {
+    fn inverse(&self, x: U256) -> Result<U256, ProgramError> {
         let n = self.order();
-        assert!(x < n);
+        if x >= n {
+            return Err(ProgramError::ProverInputError(InvalidInput));
+        };
         modexp(x, n - 2, n)
     }
 
-    fn sqrt(&self, x: U256) -> U256 {
+    fn sqrt(&self, x: U256) -> Result<U256, ProgramError> {
         let n = self.order();
-        assert!(x < n);
+        if x >= n {
+            return Err(ProgramError::ProverInputError(InvalidInput));
+        };
         let (q, r) = (n + 1).div_mod(4.into());
-        assert!(
-            r.is_zero(),
-            "Only naive sqrt implementation for now. If needed implement Tonelli-Shanks."
-        );
+
+        if !r.is_zero() {
+            return Err(ProgramError::ProverInputError(InvalidInput));
+        };
+
+        // Only naive sqrt implementation for now. If needed implement Tonelli-Shanks
         modexp(x, q, n)
     }
 
@@ -363,15 +369,18 @@ impl EvmField {
     }
 }
 
-fn modexp(x: U256, e: U256, n: U256) -> U256 {
+fn modexp(x: U256, e: U256, n: U256) -> Result<U256, ProgramError> {
     let mut current = x;
     let mut product = U256::one();
 
     for j in 0..256 {
         if e.bit(j) {
-            product = U256::try_from(product.full_mul(current) % n).unwrap();
+            product = U256::try_from(product.full_mul(current) % n)
+                .map_err(|_| ProgramError::ProverInputError(InvalidInput))?;
         }
-        current = U256::try_from(current.full_mul(current) % n).unwrap();
+        current = U256::try_from(current.full_mul(current) % n)
+            .map_err(|_| ProgramError::ProverInputError(InvalidInput))?;
     }
-    product
+
+    Ok(product)
 }
diff --git a/evm/src/generation/state.rs b/evm/src/generation/state.rs
index 2b85821f..aec01e1b 100644
--- a/evm/src/generation/state.rs
+++ b/evm/src/generation/state.rs
@@ -10,6 +10,8 @@ use crate::generation::mpt::all_mpt_prover_inputs_reversed;
 use crate::generation::rlp::all_rlp_prover_inputs_reversed;
 use crate::generation::GenerationInputs;
 use crate::memory::segments::Segment;
+use crate::util::u256_to_usize;
+use crate::witness::errors::ProgramError;
 use crate::witness::memory::{MemoryAddress, MemoryState};
 use crate::witness::state::RegistersState;
 use crate::witness::traces::{TraceCheckpoint, Traces};
@@ -49,7 +51,7 @@ pub(crate) struct GenerationState<F: Field> {
 }
 
 impl<F: Field> GenerationState<F> {
-    pub(crate) fn new(inputs: GenerationInputs, kernel_code: &[u8]) -> Self {
+    pub(crate) fn new(inputs: GenerationInputs, kernel_code: &[u8]) -> Result<Self, ProgramError> {
         log::debug!("Input signed_txns: {:?}", &inputs.signed_txns);
         log::debug!("Input state_trie: {:?}", &inputs.tries.state_trie);
         log::debug!(
@@ -59,11 +61,11 @@ impl<F: Field> GenerationState<F> {
         log::debug!("Input receipts_trie: {:?}", &inputs.tries.receipts_trie);
         log::debug!("Input storage_tries: {:?}", &inputs.tries.storage_tries);
         log::debug!("Input contract_code: {:?}", &inputs.contract_code);
-        let mpt_prover_inputs = all_mpt_prover_inputs_reversed(&inputs.tries);
+        let mpt_prover_inputs = all_mpt_prover_inputs_reversed(&inputs.tries)?;
         let rlp_prover_inputs = all_rlp_prover_inputs_reversed(&inputs.signed_txns);
         let bignum_modmul_result_limbs = Vec::new();
 
-        Self {
+        Ok(Self {
             inputs,
             registers: Default::default(),
             memory: MemoryState::new(kernel_code),
@@ -73,23 +75,25 @@ impl<F: Field> GenerationState<F> {
             rlp_prover_inputs,
             state_key_to_address: HashMap::new(),
             bignum_modmul_result_limbs,
-        }
+        })
     }
 
     /// Updates `program_counter`, and potentially adds some extra handling if we're jumping to a
     /// special location.
-    pub fn jump_to(&mut self, dst: usize) {
+    pub fn jump_to(&mut self, dst: usize) -> Result<(), ProgramError> {
         self.registers.program_counter = dst;
         if dst == KERNEL.global_labels["observe_new_address"] {
-            let tip_u256 = stack_peek(self, 0).expect("Empty stack");
+            let tip_u256 = stack_peek(self, 0)?;
             let tip_h256 = H256::from_uint(&tip_u256);
             let tip_h160 = H160::from(tip_h256);
             self.observe_address(tip_h160);
         } else if dst == KERNEL.global_labels["observe_new_contract"] {
-            let tip_u256 = stack_peek(self, 0).expect("Empty stack");
+            let tip_u256 = stack_peek(self, 0)?;
             let tip_h256 = H256::from_uint(&tip_u256);
-            self.observe_contract(tip_h256);
+            self.observe_contract(tip_h256)?;
         }
+
+        Ok(())
     }
 
     /// Observe the given address, so that we will be able to recognize the associated state key.
@@ -101,9 +105,9 @@ impl<F: Field> GenerationState<F> {
 
     /// Observe the given code hash and store the associated code.
     /// When called, the code corresponding to `codehash` should be stored in the return data.
-    pub fn observe_contract(&mut self, codehash: H256) {
+    pub fn observe_contract(&mut self, codehash: H256) -> Result<(), ProgramError> {
         if self.inputs.contract_code.contains_key(&codehash) {
-            return; // Return early if the code hash has already been observed.
+            return Ok(()); // Return early if the code hash has already been observed.
         }
 
         let ctx = self.registers.context;
@@ -112,7 +116,7 @@ impl<F: Field> GenerationState<F> {
             Segment::ContextMetadata,
             ContextMetadata::ReturndataSize as usize,
         );
-        let returndata_size = self.memory.get(returndata_size_addr).as_usize();
+        let returndata_size = u256_to_usize(self.memory.get(returndata_size_addr))?;
         let code = self.memory.contexts[ctx].segments[Segment::Returndata as usize].content
             [..returndata_size]
             .iter()
@@ -121,6 +125,8 @@ impl<F: Field> GenerationState<F> {
         debug_assert_eq!(keccak(&code), codehash);
 
         self.inputs.contract_code.insert(codehash, code);
+
+        Ok(())
     }
 
     pub fn checkpoint(&self) -> GenerationStateCheckpoint {
diff --git a/evm/src/generation/trie_extractor.rs b/evm/src/generation/trie_extractor.rs
index a508a720..42c50c6d 100644
--- a/evm/src/generation/trie_extractor.rs
+++ b/evm/src/generation/trie_extractor.rs
@@ -7,6 +7,8 @@ use ethereum_types::{BigEndianHash, H256, U256, U512};
 
 use crate::cpu::kernel::constants::trie_type::PartialTrieType;
 use crate::memory::segments::Segment;
+use crate::util::u256_to_usize;
+use crate::witness::errors::ProgramError;
 use crate::witness::memory::{MemoryAddress, MemoryState};
 
 /// Account data as it's stored in the state trie, with a pointer to the storage trie.
@@ -18,13 +20,13 @@ pub(crate) struct AccountTrieRecord {
     pub(crate) code_hash: H256,
 }
 
-pub(crate) fn read_state_trie_value(slice: &[U256]) -> AccountTrieRecord {
-    AccountTrieRecord {
+pub(crate) fn read_state_trie_value(slice: &[U256]) -> Result<AccountTrieRecord, ProgramError> {
+    Ok(AccountTrieRecord {
         nonce: slice[0].low_u64(),
         balance: slice[1],
-        storage_ptr: slice[2].as_usize(),
+        storage_ptr: u256_to_usize(slice[2])?,
         code_hash: H256::from_uint(&slice[3]),
-    }
+    })
 }
 
 pub(crate) fn read_storage_trie_value(slice: &[U256]) -> U256 {
@@ -34,72 +36,76 @@ pub(crate) fn read_storage_trie_value(slice: &[U256]) -> U256 {
 pub(crate) fn read_trie<V>(
     memory: &MemoryState,
     ptr: usize,
-    read_value: fn(&[U256]) -> V,
-) -> HashMap<Nibbles, V> {
+    read_value: fn(&[U256]) -> Result<V, ProgramError>,
+) -> Result<HashMap<Nibbles, V>, ProgramError> {
     let mut res = HashMap::new();
     let empty_nibbles = Nibbles {
         count: 0,
         packed: U512::zero(),
     };
-    read_trie_helper::<V>(memory, ptr, read_value, empty_nibbles, &mut res);
-    res
+    read_trie_helper::<V>(memory, ptr, read_value, empty_nibbles, &mut res)?;
+    Ok(res)
 }
 
 pub(crate) fn read_trie_helper<V>(
     memory: &MemoryState,
     ptr: usize,
-    read_value: fn(&[U256]) -> V,
+    read_value: fn(&[U256]) -> Result<V, ProgramError>,
     prefix: Nibbles,
     res: &mut HashMap<Nibbles, V>,
-) {
+) -> Result<(), ProgramError> {
     let load = |offset| memory.get(MemoryAddress::new(0, Segment::TrieData, offset));
     let load_slice_from = |init_offset| {
         &memory.contexts[0].segments[Segment::TrieData as usize].content[init_offset..]
     };
 
-    let trie_type = PartialTrieType::all()[load(ptr).as_usize()];
+    let trie_type = PartialTrieType::all()[u256_to_usize(load(ptr))?];
     match trie_type {
-        PartialTrieType::Empty => {}
-        PartialTrieType::Hash => {}
+        PartialTrieType::Empty => Ok(()),
+        PartialTrieType::Hash => Ok(()),
         PartialTrieType::Branch => {
             let ptr_payload = ptr + 1;
             for i in 0u8..16 {
-                let child_ptr = load(ptr_payload + i as usize).as_usize();
-                read_trie_helper::<V>(memory, child_ptr, read_value, prefix.merge_nibble(i), res);
+                let child_ptr = u256_to_usize(load(ptr_payload + i as usize))?;
+                read_trie_helper::<V>(memory, child_ptr, read_value, prefix.merge_nibble(i), res)?;
             }
-            let value_ptr = load(ptr_payload + 16).as_usize();
+            let value_ptr = u256_to_usize(load(ptr_payload + 16))?;
             if value_ptr != 0 {
-                res.insert(prefix, read_value(load_slice_from(value_ptr)));
+                res.insert(prefix, read_value(load_slice_from(value_ptr))?);
             };
+
+            Ok(())
         }
         PartialTrieType::Extension => {
-            let count = load(ptr + 1).as_usize();
+            let count = u256_to_usize(load(ptr + 1))?;
             let packed = load(ptr + 2);
             let nibbles = Nibbles {
                 count,
                 packed: packed.into(),
             };
-            let child_ptr = load(ptr + 3).as_usize();
+            let child_ptr = u256_to_usize(load(ptr + 3))?;
             read_trie_helper::<V>(
                 memory,
                 child_ptr,
                 read_value,
                 prefix.merge_nibbles(&nibbles),
                 res,
-            );
+            )
         }
         PartialTrieType::Leaf => {
-            let count = load(ptr + 1).as_usize();
+            let count = u256_to_usize(load(ptr + 1))?;
             let packed = load(ptr + 2);
             let nibbles = Nibbles {
                 count,
                 packed: packed.into(),
             };
-            let value_ptr = load(ptr + 3).as_usize();
+            let value_ptr = u256_to_usize(load(ptr + 3))?;
             res.insert(
                 prefix.merge_nibbles(&nibbles),
-                read_value(load_slice_from(value_ptr)),
+                read_value(load_slice_from(value_ptr))?,
             );
+
+            Ok(())
         }
     }
 }
diff --git a/evm/src/recursive_verifier.rs b/evm/src/recursive_verifier.rs
index 1457344c..113dd287 100644
--- a/evm/src/recursive_verifier.rs
+++ b/evm/src/recursive_verifier.rs
@@ -935,7 +935,7 @@ where
         witness,
         &public_values_target.extra_block_data,
         &public_values.extra_block_data,
-    );
+    )?;
 
     Ok(())
 }
@@ -1072,26 +1072,21 @@ pub(crate) fn set_extra_public_values_target<F, W, const D: usize>(
     witness: &mut W,
     ed_target: &ExtraBlockDataTarget,
     ed: &ExtraBlockData,
-) where
+) -> Result<(), ProgramError>
+where
     F: RichField + Extendable<D>,
     W: Witness<F>,
 {
     witness.set_target(
         ed_target.txn_number_before,
-        F::from_canonical_usize(ed.txn_number_before.as_usize()),
+        u256_to_u32(ed.txn_number_before)?,
     );
     witness.set_target(
         ed_target.txn_number_after,
-        F::from_canonical_usize(ed.txn_number_after.as_usize()),
-    );
-    witness.set_target(
-        ed_target.gas_used_before,
-        F::from_canonical_usize(ed.gas_used_before.as_usize()),
-    );
-    witness.set_target(
-        ed_target.gas_used_after,
-        F::from_canonical_usize(ed.gas_used_after.as_usize()),
+        u256_to_u32(ed.txn_number_after)?,
     );
+    witness.set_target(ed_target.gas_used_before, u256_to_u32(ed.gas_used_before)?);
+    witness.set_target(ed_target.gas_used_after, u256_to_u32(ed.gas_used_after)?);
 
     let block_bloom_before = ed.block_bloom_before;
     let mut block_bloom_limbs = [F::ZERO; 64];
@@ -1108,4 +1103,6 @@ pub(crate) fn set_extra_public_values_target<F, W, const D: usize>(
     }
 
     witness.set_target_arr(&ed_target.block_bloom_after, &block_bloom_limbs);
+
+    Ok(())
 }
diff --git a/evm/src/util.rs b/evm/src/util.rs
index a3f6d050..08233056 100644
--- a/evm/src/util.rs
+++ b/evm/src/util.rs
@@ -70,6 +70,11 @@ pub(crate) fn u256_to_u64<F: Field>(u256: U256) -> Result<(F, F), ProgramError>
     ))
 }
 
+/// Safe alternative to `U256::as_usize()`, which errors in case of overflow instead of panicking.
+pub(crate) fn u256_to_usize(u256: U256) -> Result<usize, ProgramError> {
+    u256.try_into().map_err(|_| ProgramError::IntegerTooLarge)
+}
+
 #[allow(unused)] // TODO: Remove?
 /// Returns the 32-bit little-endian limbs of a `U256`.
 pub(crate) fn u256_limbs<F: Field>(u256: U256) -> [F; 8] {
@@ -171,6 +176,8 @@ pub(crate) fn u256_to_biguint(x: U256) -> BigUint {
 
 pub(crate) fn biguint_to_u256(x: BigUint) -> U256 {
     let bytes = x.to_bytes_le();
+    // This could panic if `bytes.len() > 32` but this is only
+    // used here with `BigUint` constructed from `U256`.
     U256::from_little_endian(&bytes)
 }
 
diff --git a/evm/src/witness/errors.rs b/evm/src/witness/errors.rs
index 1ab99eae..81862460 100644
--- a/evm/src/witness/errors.rs
+++ b/evm/src/witness/errors.rs
@@ -6,6 +6,7 @@ pub enum ProgramError {
     OutOfGas,
     InvalidOpcode,
     StackUnderflow,
+    InvalidRlp,
     InvalidJumpDestination,
     InvalidJumpiDestination,
     StackOverflow,
@@ -14,6 +15,8 @@ pub enum ProgramError {
     GasLimitError,
     InterpreterError,
     IntegerTooLarge,
+    ProverInputError(ProverInputError),
+    UnknownContractCode,
 }
 
 #[allow(clippy::enum_variant_names)]
@@ -23,3 +26,13 @@ pub enum MemoryError {
     SegmentTooLarge { segment: U256 },
     VirtTooLarge { virt: U256 },
 }
+
+#[derive(Debug)]
+pub enum ProverInputError {
+    OutOfMptData,
+    OutOfRlpData,
+    CodeHashNotFound,
+    InvalidMptInput,
+    InvalidInput,
+    InvalidFunction,
+}
diff --git a/evm/src/witness/memory.rs b/evm/src/witness/memory.rs
index 62e6a2fe..3b62c945 100644
--- a/evm/src/witness/memory.rs
+++ b/evm/src/witness/memory.rs
@@ -58,6 +58,8 @@ impl MemoryAddress {
         if virt.bits() > 32 {
             return Err(MemoryError(VirtTooLarge { virt }));
         }
+
+        // Calling `as_usize` here is safe as those have been checked above.
         Ok(Self {
             context: context.as_usize(),
             segment: segment.as_usize(),
diff --git a/evm/src/witness/operation.rs b/evm/src/witness/operation.rs
index 8349d56d..2abeaea4 100644
--- a/evm/src/witness/operation.rs
+++ b/evm/src/witness/operation.rs
@@ -15,6 +15,7 @@ use crate::cpu::stack_bounds::MAX_USER_STACK_SIZE;
 use crate::extension_tower::BN_BASE;
 use crate::generation::state::GenerationState;
 use crate::memory::segments::Segment;
+use crate::util::u256_to_usize;
 use crate::witness::errors::MemoryError::{ContextTooLarge, SegmentTooLarge, VirtTooLarge};
 use crate::witness::errors::ProgramError;
 use crate::witness::errors::ProgramError::MemoryError;
@@ -127,7 +128,7 @@ pub(crate) fn generate_keccak_general<F: Field>(
     row.is_keccak_sponge = F::ONE;
     let [(context, log_in0), (segment, log_in1), (base_virt, log_in2), (len, log_in3)] =
         stack_pop_with_log_and_fill::<4, _>(state, &mut row)?;
-    let len = len.as_usize();
+    let len = u256_to_usize(len)?;
 
     let base_address = MemoryAddress::new_u256s(context, segment, base_virt)?;
     let input = (0..len)
@@ -162,7 +163,7 @@ pub(crate) fn generate_prover_input<F: Field>(
 ) -> Result<(), ProgramError> {
     let pc = state.registers.program_counter;
     let input_fn = &KERNEL.prover_inputs[&pc];
-    let input = state.prover_input(input_fn);
+    let input = state.prover_input(input_fn)?;
     let write = stack_push_log_and_fill(state, &mut row, input)?;
 
     state.traces.push_memory(write);
@@ -217,7 +218,7 @@ pub(crate) fn generate_jump<F: Field>(
 
     state.traces.push_memory(log_in0);
     state.traces.push_cpu(row);
-    state.jump_to(dst as usize);
+    state.jump_to(dst as usize)?;
     Ok(())
 }
 
@@ -241,7 +242,7 @@ pub(crate) fn generate_jumpi<F: Field>(
         let dst: u32 = dst
             .try_into()
             .map_err(|_| ProgramError::InvalidJumpiDestination)?;
-        state.jump_to(dst as usize);
+        state.jump_to(dst as usize)?;
     } else {
         row.general.jumps_mut().should_jump = F::ZERO;
         row.general.jumps_mut().cond_sum_pinv = F::ZERO;
@@ -312,7 +313,7 @@ pub(crate) fn generate_set_context<F: Field>(
     let [(ctx, log_in)] = stack_pop_with_log_and_fill::<1, _>(state, &mut row)?;
     let sp_to_save = state.registers.stack_len.into();
     let old_ctx = state.registers.context;
-    let new_ctx = ctx.as_usize();
+    let new_ctx = u256_to_usize(ctx)?;
 
     let sp_field = ContextMetadata::StackSize as usize;
     let old_sp_addr = MemoryAddress::new(old_ctx, Segment::ContextMetadata, sp_field);
@@ -347,7 +348,8 @@ pub(crate) fn generate_set_context<F: Field>(
     };
 
     state.registers.context = new_ctx;
-    state.registers.stack_len = new_sp.as_usize();
+    let new_sp = u256_to_usize(new_sp)?;
+    state.registers.stack_len = new_sp;
     state.traces.push_memory(log_in);
     state.traces.push_memory(log_write_old_sp);
     state.traces.push_memory(log_read_new_sp);
@@ -362,6 +364,10 @@ pub(crate) fn generate_push<F: Field>(
 ) -> Result<(), ProgramError> {
     let code_context = state.registers.code_context();
     let num_bytes = n as usize;
+    if num_bytes > 32 {
+        // The call to `U256::from_big_endian()` would panic.
+        return Err(ProgramError::IntegerTooLarge);
+    }
     let initial_offset = state.registers.program_counter + 1;
 
     // First read val without going through `mem_read_with_log` type methods, so we can pass it
@@ -589,7 +595,7 @@ pub(crate) fn generate_syscall<F: Field>(
     );
 
     let handler_addr = (handler_addr0 << 16) + (handler_addr1 << 8) + handler_addr2;
-    let new_program_counter = handler_addr.as_usize();
+    let new_program_counter = u256_to_usize(handler_addr)?;
 
     let syscall_info = U256::from(state.registers.program_counter + 1)
         + (U256::from(u64::from(state.registers.is_kernel)) << 32)
@@ -694,7 +700,11 @@ pub(crate) fn generate_mload_32bytes<F: Field>(
 ) -> Result<(), ProgramError> {
     let [(context, log_in0), (segment, log_in1), (base_virt, log_in2), (len, log_in3)] =
         stack_pop_with_log_and_fill::<4, _>(state, &mut row)?;
-    let len = len.as_usize();
+    let len = u256_to_usize(len)?;
+    if len > 32 {
+        // The call to `U256::from_big_endian()` would panic.
+        return Err(ProgramError::IntegerTooLarge);
+    }
 
     let base_address = MemoryAddress::new_u256s(context, segment, base_virt)?;
     if usize::MAX - base_address.virt < len {
@@ -762,7 +772,7 @@ pub(crate) fn generate_mstore_32bytes<F: Field>(
 ) -> Result<(), ProgramError> {
     let [(context, log_in0), (segment, log_in1), (base_virt, log_in2), (val, log_in3), (len, log_in4)] =
         stack_pop_with_log_and_fill::<5, _>(state, &mut row)?;
-    let len = len.as_usize();
+    let len = u256_to_usize(len)?;
 
     let base_address = MemoryAddress::new_u256s(context, segment, base_virt)?;
 
@@ -827,7 +837,7 @@ pub(crate) fn generate_exception<F: Field>(
     );
 
     let handler_addr = (handler_addr0 << 16) + (handler_addr1 << 8) + handler_addr2;
-    let new_program_counter = handler_addr.as_usize();
+    let new_program_counter = u256_to_usize(handler_addr)?;
 
     let exc_info =
         U256::from(state.registers.program_counter) + (U256::from(state.registers.gas_used) << 192);
diff --git a/evm/src/witness/util.rs b/evm/src/witness/util.rs
index 94488614..068a8e11 100644
--- a/evm/src/witness/util.rs
+++ b/evm/src/witness/util.rs
@@ -29,11 +29,14 @@ fn to_bits_le<F: Field>(n: u8) -> [F; 8] {
 }
 
 /// Peek at the stack item `i`th from the top. If `i=0` this gives the tip.
-pub(crate) fn stack_peek<F: Field>(state: &GenerationState<F>, i: usize) -> Option<U256> {
+pub(crate) fn stack_peek<F: Field>(
+    state: &GenerationState<F>,
+    i: usize,
+) -> Result<U256, ProgramError> {
     if i >= state.registers.stack_len {
-        return None;
+        return Err(ProgramError::StackUnderflow);
     }
-    Some(state.memory.get(MemoryAddress::new(
+    Ok(state.memory.get(MemoryAddress::new(
         state.registers.context,
         Segment::Stack,
         state.registers.stack_len - 1 - i,