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

# Function get_auth_witness_as_bytes

Module: `noir_aztec::oracle::auth_witness`

```rust
pub unconstrained fn get_auth_witness_as_bytes<let N: u32>(
    message_hash: Field,
) -> [u8; N]
```

Fetches an auth witness and casts each field to a byte.

Each field is range-checked to `[0, 256)` before casting to prevent silent truncation (e.g. a field value of `b + 256` would truncate to the same byte as `b`).