> Aztec.nr API reference, v6.0.0 (mainnet and testnet). Index: https://docs.aztec.network/aztec-nr-api/v6.0.0/llms.txt

# Module nullifier

Module: `noir_aztec::history::nullifier`

Nullifier existence and non-existence.

## Functions

- [assert_nullifier_did_not_exist_by](/aztec-nr-api/v6.0.0/noir_aztec/history/nullifier/fn.assert_nullifier_did_not_exist_by.md): Asserts that a nullifier did not exist by the time a block was mined.
- [assert_nullifier_existed_by](/aztec-nr-api/v6.0.0/noir_aztec/history/nullifier/fn.assert_nullifier_existed_by.md): Asserts that a nullifier existed by the time a block was mined.