HKDF
=====
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An implementation of [HKDF](https://tools.ietf.org/html/rfc5869) in Erlang.

Requirements
-----

 - `Erlang 22+`

Usage
-----

#### derive key
```erlang
OKM = hkdf:derive(sha384, <<"Never gonna give you up">>, 42).
```

#### extract key
```erlang
PRK = hkdf:extract(sha384, <<"Never gonna give you up">>).
```

#### expand key
```erlang
PRK = hkdf:extract(sha384, <<"Never gonna give you up">>).
OKM = hkdf:expand(sha384, PRK, 42).
```