# HASH

`HASH` hashes `value` using the hashing algorithm given in `algorithm` (accepted values `SHA1`, `SHA256`, and `SHA512`) and returns the hex encoded hash value.

example `HASH("SHA1", "abc")` returns `a9993e364706816aba3e25717850c26c9cd0d89d`.

`HASH()`'s primary use case is for managing [catalog zones](https://datatracker.ietf.org/doc/html/rfc9432):

> a method for automatic DNS zone provisioning among DNS primary and secondary name servers by storing and transferring the catalog of zones to be provisioned as one or more regular DNS zones.

Here's an example of a catalog zone:

{% code title="dnsconfig.js" %}

```javascript
foo_name_suffix = HASH("SHA1", "foo.name") + ".zones"
D("catalog.example"
    [...]
    , TXT("version", "2")
    , PTR(foo_name_suffix, "foo.name.")
    , A("primaries.ext." + foo_name_suffix, "192.168.1.1")
)
```

{% endcode %}