Cryptography

This document is better viewed at https://docs.openzeppelin.com/contracts/api/cryptography

This collection of libraries provides simple and safe ways to use different cryptographic primitives.

The following related EIPs are in draft status and can be found in the drafts directory.

Libraries

ECDSA

Elliptic Curve Digital Signature Algorithm (ECDSA) operations.

These functions can be used to verify that a message was signed by the holder of the private keys of a given address.

Functions

recover(bytes32 hash, bytes signature) → address internal

Returns the address that signed a hashed message (hash) with signature. This address can then be used for verification purposes.

The ecrecover EVM opcode allows for malleable (non-unique) signatures: this function rejects them by requiring the s value to be in the lower half order, and the v value to be either 27 or 28.

hash must be the result of a hash operation for the verification to be secure: it is possible to craft signatures that recover to arbitrary addresses for non-hashed data. A safe way to ensure this is by receiving a hash of the original message (which may otherwise be too long), and then calling toEthSignedMessageHash on it.

recover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) → address internal

Overload of {ECDSA-recover-bytes32-bytes-} that receives the v, r and s signature fields separately.

toEthSignedMessageHash(bytes32 hash) → bytes32 internal

Returns an Ethereum Signed Message, created from a hash. This replicates the behavior of the eth_sign JSON-RPC method.

See recover. /

MerkleProof

These functions deal with verification of Merkle trees (hash trees),

Functions

verify(bytes32[] proof, bytes32 root, bytes32 leaf) → bool internal

Returns true if a leaf can be proved to be a part of a Merkle tree defined by root. For this, a proof must be provided, containing sibling hashes on the branch from the leaf to the root of the tree. Each pair of leaves and each pair of pre-images are assumed to be sorted.

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