Module solana_libra_crypto::hash

This module defines traits and implementations of cryptographic hash functions for the Libra project.

It is designed to help authors protect against two types of real world attacks:

1. Domain Ambiguity: imagine that Alice has a private key and is using two different applications, X and Y. X asks Alice to sign a message saying "I am Alice". naturally, Alice is willing to sign this message, since she is in fact Alice. However, unbeknownst to Alice, in application Y, messages beginning with the letter "I" represent transfers. " am " represents a transfer of 500 coins and "Alice" can be interpreted as a destination address. When Alice signed the message she needed to be aware of how other applications might interpret that message.

2. Format Ambiguity: imagine a program that hashes a pair of strings. To hash the strings a and b it hashes a + "||" + b. The pair of strings a="foo||", b = "bar" and a="foo", b = "||bar" result in the same input to the hash function and therefore the same hash. This creates a collision.

Examples

use solana_libra_crypto::hash::{CryptoHasher, TestOnlyHasher};

let mut hasher = TestOnlyHasher::default();
hasher.write("Test message".as_bytes());
let hash_value = hasher.finish();

The output is of type HashValue, which can be used as an input for signing.

Implementing new hashers

For any new structure MyNewStruct that needs to be hashed, the developer should define a new hasher with:

define_hasher! { (MyNewStructHasher, MY_NEW_STRUCT_HASHER, b"MyNewStruct") }

Note: The last argument for the define_hasher macro must be a unique string.

Then, the CryptoHash trait should be implemented:

struct MyNewStruct;

impl CryptoHash for MyNewStruct {
    type Hasher = MyNewStructHasher; // use the above defined hasher here

    fn hash(&self) -> HashValue {
        let mut state = Self::Hasher::default();
        state.write(b"Struct serialized into bytes here");
        state.finish()
    }
}

Structs

ACCUMULATOR_PLACEHOLDER_HASH	Placeholder hash of Accumulator.
AccessPathHasher	The hasher used to compute the hash of an AccessPath object.
AccountAddressHasher	The hasher used to compute the hash of an AccountAddress object.
AccountStateBlobHasher	The hasher used to compute the hash of the blob content of an account.
BlockHasher	The hasher used to compute the hash (block_id) of a Block object.
ContractEventHasher	The hasher used to compute the hash of a ContractEvent object.
DiscoveryMsgHasher	The hasher used to compute the hash of a DiscoveryMsg object.
EventAccumulatorHasher	The hasher used to compute the hash of an internal node in the event accumulator.
GENESIS_BLOCK_ID	Genesis block id is used as a parent of the very first block executed by the executor.
HashValue	Output value of our hash function. Intentionally opaque for safety and modularity.
HashValueBitIterator	An iterator over HashValue that generates one bit for each iteration.
LedgerInfoHasher	The hasher used to compute the hash of a LedgerInfo object.
PRE_GENESIS_BLOCK_ID	Block id reserved as the id of parent block of the genesis block.
PacemakerTimeoutHasher	The hasher used to compute the hash of a PacemakerTimeout object.
RawTransactionHasher	The hasher used to compute the hash of a RawTransaction object.
RoundHasher	The hasher used to compute the hash of a Round
SPARSE_MERKLE_PLACEHOLDER_HASH	Placeholder hash of SparseMerkleTree.
SignedTransactionHasher	The hasher used to compute the hash of a SignedTransaction object.
SparseMerkleInternalHasher	The hasher used to compute the hash of an internal node in the Sparse Merkle Tree.
SparseMerkleLeafHasher	The hasher used to compute the hash of a leaf node in the Sparse Merkle Tree.
TestOnlyHasher	The hasher used only for testing. It doesn't have a salt.
TimeoutMsgHasher	The hasher used to compute the hash of a TimeoutMsgHasher object.
TransactionAccumulatorHasher	The hasher used to compute the hash of an internal node in the transaction accumulator.
TransactionInfoHasher	The hasher used to compute the hash of a TransactionInfo object.
VoteDataHasher	The hasher used to compute the hash of a VoteData object.

Traits

CryptoHash	A type that implements CryptoHash can be hashed by a cryptographic hash function and produce a HashValue. Each type needs to have its own Hasher type.
CryptoHasher	A trait for generating hash from arbitrary stream of bytes.
TestOnlyHash	Provides a test_only_hash() method that can be used in tests on types that implement serde::Serialize.