Cryptography
Outdated Version
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.
- EIP712
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.