MultiversX Crypto Verification — `self.crypto()` API Reference Skill

MultiversX Crypto Verification — `self.crypto()` API Reference

Complete reference for hashing and signature verification in MultiversX smart contracts (SDK v0.64+).

Hashing Functions

All hashing functions take &ManagedBuffer (or anything that borrows as ManagedBuffer) and return a fixed-size ManagedByteArray.

| Method | Return Type | Output Size | Use Case | |--------|------------|-------------|----------| | .sha256(data) | ManagedByteArray<A, 32> | 32 bytes | General purpose hashing, Merkle trees | | .keccak256(data) | ManagedByteArray<A, 32> | 32 bytes | Ethereum compatibility, EIP-712 | | .ripemd160(data) | ManagedByteArray<A, 20> | 20 bytes | Bitcoin address derivation (rare) |

// Hash a message
let message = ManagedBuffer::from("data to hash");
let hash: ManagedByteArray<Self::Api, 32> = self.crypto().sha256(&message);

// Hash for Ethereum compatibility
let eth_hash = self.crypto().keccak256(&abi_encoded_data);

Signature Verification

Critical Distinction: Panic vs Bool

Panic-based — Transaction fails immediately on invalid signature. No error handling possible. Use when invalid signature = unauthorized action.

Bool-based — Returns true/false. Contract continues execution. Use when you need graceful error handling or multiple verification attempts.

| Method | Returns | On Invalid Signature | |--------|---------|---------------------| | verify_ed25519(key, message, signature) | () | Panics — tx fails with "invalid signature" | | verify_bls(key, message, signature) | () | Panics | | verify_secp256r1(key, message, signature) | () | Panics | | verify_bls_signature_share(key, message, signature) | () | Panics | | verify_bls_aggregated_signature(keys, message, signature) | () | Panics | | verify_secp256k1(key, message, signature) | bool | Returns false | | verify_custom_secp256k1(key, message, signature, hash_type) | bool | Returns false |

Method Signatures

// Panic-based (no return value)
fn verify_ed25519(
    &self,
    key: &ManagedBuffer<A>,       // 32-byte public key
    message: &ManagedBuffer<A>,   // arbitrary message
    signature: &ManagedBuffer<A>, // 64-byte signature
)

fn verify_bls(
    &self,
    key: &ManagedBuffer<A>,       // 96-byte BLS public key
    message: &ManagedBuffer<A>,
    signature: &ManagedBuffer<A>, // 48-byte BLS signature
)

fn verify_secp256r1(
    &self,
    key: &ManagedBuffer<A>,       // 33 or 65-byte public key
    message: &ManagedBuffer<A>,
    signature: &ManagedBuffer<A>,
)

fn verify_bls_signature_share(
    &self,
    key: &ManagedBuffer<A>,
    message: &ManagedBuffer<A>,
    signature: &ManagedBuffer<A>,
)

fn verify_bls_aggregated_signature(
    &self,
    keys: &ManagedVec<A, ManagedBuffer<A>>,  // list of BLS public keys
    message: &ManagedBuffer<A>,
    signature: &ManagedBuffer<A>,             // aggregated signature
)

// Bool-based
fn verify_secp256k1(
    &self,
    key: &ManagedBuffer<A>,
    message: &ManagedBuffer<A>,
    signature: &ManagedBuffer<A>,  // DER-encoded or raw (min 2 bytes)
) -> bool

fn verify_custom_secp256k1(
    &self,
    key: &ManagedBuffer<A>,
    message: &ManagedBuffer<A>,
    signature: &ManagedBuffer<A>,
    hash_type: MessageHashType,    // how the message was hashed
) -> bool

MessageHashType Enum

Used with verify_custom_secp256k1 to specify how the message was pre-hashed:

pub enum MessageHashType {
    ECDSAPlainMsg,      // Message is not hashed (raw)
    ECDSASha256,        // Message was SHA-256 hashed
    ECDSADoubleSha256,  // Message was double SHA-256 hashed (Bitcoin)
    ECDSAKeccak256,     // Message was Keccak-256 hashed (Ethereum)
    ECDSARipemd160,     // Message was RIPEMD-160 hashed
    ECDSABlake2b,       // Message was Blake2b hashed
}

DER Signature Encoding

Convert raw (r, s) components to DER format for secp256k1:

fn encode_secp256k1_der_signature(
    &self,
    r: &ManagedBuffer<A>,  // 32-byte r component
    s: &ManagedBuffer<A>,  // 32-byte s component
) -> ManagedBuffer<A>      // DER-encoded signature

Algorithm Selection Guide

| Algorithm | When to Use | |-----------|-------------| | Ed25519 | MultiversX native signatures. Verify user/SC signatures from the chain. Default choice. | | secp256k1 | Ethereum/Bitcoin compatibility. Bridge contracts, cross-chain verification. | | secp256r1 | NIST P-256 / WebAuthn / Apple Secure Enclave. Passkey-based auth. | | BLS | Validator signatures, multi-sig aggregation, threshold schemes. | | BLS aggregated | Verify a single aggregated signature from multiple validators. |

Common Patterns

Ed25519 Signature Gate (MultiversX Native)

#[endpoint(executeWithSignature)]
fn execute_with_signature(
    &self,
    data: ManagedBuffer,
    signature: ManagedBuffer,
) {
    let signer = self.trusted_signer().get();
    // Panics if invalid — tx reverts automatically
    self.crypto().verify_ed25519(
        &signer,
        &data,
        &signature,
    );
    // Only reached if signature is valid
    self.process_data(&data);
}

Ethereum Signature Verification (Graceful)

#[endpoint(verifyEthSignature)]
fn verify_eth_signature(
    &self,
    key: ManagedBuffer,
    message: ManagedBuffer,
    signature: ManagedBuffer,
) -> bool {
    // Returns bool — handle failure gracefully
    let valid = self.crypto().verify_custom_secp256k1(
        &key,
        &message,
        &signature,
        MessageHashType::ECDSAKeccak256,
    );
    require!(valid, "Invalid Ethereum signature");
    valid
}

Multi-Validator BLS Aggregated Check

#[endpoint(verifyValidators)]
fn verify_validators(
    &self,
    validator_keys: ManagedVec<ManagedBuffer>,
    message: ManagedBuffer,
    aggregated_sig: ManagedBuffer,
) {
    // Panics if aggregated signature is invalid
    self.crypto().verify_bls_aggregated_signature(
        &validator_keys,
        &message,
        &aggregated_sig,
    );
}

Hash-Based Commit-Reveal

#[endpoint(commit)]
fn commit(&self, hash: ManagedByteArray<Self::Api, 32>) {
    let caller = self.blockchain().get_caller();
    self.commitments(&caller).set(hash);
}

#[endpoint(reveal)]
fn reveal(&self, value: ManagedBuffer) {
    let caller = self.blockchain().get_caller();
    let stored_hash = self.commitments(&caller).get();
    let computed_hash = self.crypto().sha256(&value);
    require!(stored_hash == computed_hash, "Hash mismatch");
    self.commitments(&caller).clear();
    self.process_reveal(&caller, &value);
}

DER Encoding for secp256k1

// When you have raw r,s components (e.g., from an oracle)
let r = ManagedBuffer::from(&r_bytes[..]);
let s = ManagedBuffer::from(&s_bytes[..]);
let der_sig = self.crypto().encode_secp256k1_der_signature(&r, &s);

let valid = self.crypto().verify_secp256k1(&pubkey, &message, &der_sig);

Anti-Patterns

// BAD: Trying to catch Ed25519 failure — it panics, there's nothing to catch
let result = self.crypto().verify_ed25519(&key, &msg, &sig);
// ← verify_ed25519 returns (), not Result. If invalid, tx is already dead.

// GOOD: Use Ed25519 as a gate (panic is the intended behavior)
self.crypto().verify_ed25519(&key, &msg, &sig);
// Execution continues only if valid

// BAD: Using verify_secp256k1 without checking the bool
self.crypto().verify_secp256k1(&key, &msg, &sig);
// ← Compiles fine but ignores the result! Signature not actually checked.

// GOOD: Always check the bool return
let valid = self.crypto().verify_secp256k1(&key, &msg, &sig);
require!(valid, "Invalid signature");

// BAD: Using wrong hash type for Ethereum signatures
self.crypto().verify_custom_secp256k1(&key, &msg, &sig, MessageHashType::ECDSASha256);
// ← Ethereum uses Keccak256, not SHA256

// GOOD: Match the hash type to the chain
self.crypto().verify_custom_secp256k1(&key, &msg, &sig, MessageHashType::ECDSAKeccak256);

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