# Zebra Shielded Scanning

This document describes how expert users can try Zebra's shielded scanning feature.

For now, we only support Sapling, and only store transaction IDs in the scanner results database.
Ongoing development is tracked in issue [#7728](https://github.com/ZcashFoundation/zebra/issues/7728).

## Important Security Warning

Zebra's shielded scanning feature has known security issues. It is for experimental use only.

Do not use regular or sensitive viewing keys with Zebra's experimental scanning feature. Do not use this feature on a shared machine. We suggest generating new keys for experimental use.

## Build & Install

- Clone a Zebra version greater than or equal to [1.5.0](https://github.com/ZcashFoundation/zebra/releases/tag/v1.5.0) or use the `main` branch to get the latest features.

```bash
cargo install --features shielded-scan --locked --git https://github.com/ZcashFoundation/zebra zebrad
```
Zebra binary will be at `~/.cargo/bin/zebrad`.

- Generate a configuration file with the default settings:

```bash
zebrad generate -o ~/.config/zebrad.toml
```

## Configuration

In `zebrad.toml`, use:
- the `[shielded_scan]` table for database settings, and
- the `[shielded_scan.sapling_keys_to_scan]` table for diversifiable full viewing keys.

Sapling diversifiable/extended full viewing keys strings start with `zxviews` as described in [ZIP-32](https://zips.z.cash/zip-0032#sapling-extended-full-viewing-keys).

For example, to scan for transactions with the [public ZECpages viewing key](https://zecpages.com/boardinfo) use:

```toml
[shielded_scan.sapling_keys_to_scan]
"zxviews1q0duytgcqqqqpqre26wkl45gvwwwd706xw608hucmvfalr759ejwf7qshjf5r9aa7323zulvz6plhttp5mltqcgs9t039cx2d09mgq05ts63n8u35hyv6h9nc9ctqqtue2u7cer2mqegunuulq2luhq3ywjcz35yyljewa4mgkgjzyfwh6fr6jd0dzd44ghk0nxdv2hnv4j5nxfwv24rwdmgllhe0p8568sgqt9ckt02v2kxf5ahtql6s0ltjpkckw8gtymxtxuu9gcr0swvz" = 419200
```

Where the number `1` above is the birthday of the corresponding key:
- birthday lower than the sapling activation height defaults to sapling activation height.
- birthday greater or equal than sapling activation height will start scanning at provided height, improving scanner speed.

## Running Sapling Scanning

For full scanning results. launch Zebra and wait for 12-24 hours. Zebra needs to be synced up to at least the Sapling activation height to start scanning. If you have an already synced-up chain, the scanner will start looking for transactions for the provided keys from the start.

```bash
zebrad
```

You should see log messages in the output every 10000 blocks scanned, similar to:

```
2023-12-16T12:14:41.526740Z  INFO zebra_scan::storage::db: Last scanned height for key number 0 is 435000, resuming at 435001
2023-12-16T12:14:41.526745Z  INFO zebra_scan::storage::db: loaded Zebra scanner cache
...
2023-12-16T12:15:19.063796Z  INFO {zebrad="39830b0" net="Main"}: zebra_scan::scan: Scanning the blockchain for key 0, started at block 435001, now at block 440000, current tip 2330550
...
```

The Zebra scanner will resume the task if your Zebra instance went down for any reason. In a new start, Zebra will display:

```
Last scanned height for key number 0 is 1798000, resuming at 1798001
```

## Querying results with the `scanning-results-reader` utility.

The easier way to read the results of found transactions and more is to use the utility tool named `scanning-results-reader`. Please read the [tool description](https://github.com/ZcashFoundation/zebra/tree/main/zebra-utils#scanning-results-reader) to learn how to use it. Instructions are straightforward.

## Querying Raw Sapling Scanning Results

A more advanced way to query results is to use `ldb` tool, requires a certain level of expertise.

Install `ldb`:

```bash
sudo apt install rocksdb-tools
```

Run `ldb` with the scanner database:

```bash
ldb --db="$HOME/.cache/zebra/private-scan/v1/mainnet" --secondary_path= --column_family=sapling_tx_ids --hex scan
```

Some of the output will be markers the scanner uses to keep track of progress, however, some of them will be transactions found.

To lean more about how to filter the database please refer to [RocksDB Administration and Data Access Tool](https://github.com/facebook/rocksdb/wiki/Administration-and-Data-Access-Tool)