Data

Tools

Indexes

Applications

Experiments

Awesome

An open API service indexing awesome lists of open source software.

https://github.com/propensive/gastronomy

Simple generically-derived cryptographic functions for Scala
https://github.com/propensive/gastronomy

cryptographic-digests cryptography digest encryption hash md5 scala sha2 sha256

Last synced: about 1 year ago
JSON representation

Simple generically-derived cryptographic functions for Scala

Awesome Lists containing this project

README 

          
[GitHub Workflow](https://github.com/propensive/gastronomy/actions)

[](https://discord.com/invite/MBUrkTgMnA)




# Gastronomy



__Simple generically-derived cryptographic digestion__



Gastronomy provides a range of common cryptographic operations through a simple, typesafe and

immutable API.



## Features



- hashing of simple and primitive Scala types

- generically-derived digests for all product and coproduct types

- supports SHA-256, SHA-1 and MD5 hash algorithms

- symmetric encryption with AES

- asymmetric encryption/decryption using RSA

- signing with DSA

- AES, RSA and DSA key generation

- calculation of HMACs for SHA-256, SHA-1 and MD5

- encoding into Hex, BASE-64, and URL-safe BASE-64

- serializers and parsers for PEM-encoded data



## Availability



## Getting Started



All Gastronomy terms and types are defined in the `gastronomy` package:

```scala

import gastronomy.*

```

and exported to the `soundness` package:

```scala

import soundness.*

```



__Gastronomy__ provides representations of public, private and symmetric keys which offer a number

of cryptographic methods:



- `PublicKey` provides:

  - `verify` for verifying signatures

  - `encrypt` for encrypting data

  - `pem` to provide the public key as a PEM-encoded string

- `PrivateKey` provides:

  - `sign` for signing data

  - `decrypt` for decrypting encrypted data

  - `public` to derive a `PublicKey` from the `PrivateKey`

  - `pem` to provide the private key as a PEM-encoded string

- `SymmetricKey` provides `verify`, `encrypt`, `pem`, `sign` and `decrypt` in a single key.



Additionally, the extension methods, `digest` and `hmac` are provided for any value which can be

serialized to bytes.



The objects `PrivateKey` and `SymmetricKey` both have `generate` methods which will generate new

random keys.



### Signing



Given, for example, a `PrivateKey[Dsa[1024]]` instance, `key`, data may be signed with, for example,

```scala

val key: PrivateKey[Dsa[1024]] = ???

val signature: Signature[Dsa[1024]] = key.sign(data)

```

This works for any value, `data`, that has an appropriate `ByteCodec` instance. The type parameter

of the signature will depend on the type parameter of the private key.



### Verifying a signature



A public key, `pubKey`, which could, for example, be derived from the private key in the previous

example,

```scala

val pubKey = key.public

```

may be used to verify a signature of type `Signature[Dsa[1024]]` with:

```scala

val valid: Boolean = pubKey.verify(data, signature)

```



Here, `data` must be the same object that was used (with the private key) to produce the signature,

and may be any type that has a contextual `ByteCodec` instance.



### Encryption



A public key instance, for example, `pubKey` of type `PublicKey[Rsa[2048]]`, can encrypt some data

by calling,

```scala

val encrypted: Message[Rsa[2048]] = pubKey.encrypt(data)

```



### Decryption



An encrypted message may conversely be decrypted using the corresponding `PrivateKey[Rsa[2048]]`

instance, `key`:

```scala

val data: String = key.decrypt[String](encrypted)

```



The return type (`String` in the above example) must be specified as a parameter to the `decrypt`

method, and may be any type for which a corresponding `ByteCodec` exists in context. However, the

type should be the same as the type of the object that was originally encrypted, otherwise it may

fail to decode.



### Digests



A cryptographic digest (or hash) of any value may be calculated by calling `digest[A]` on that

value, for an appropriate choice of `A`, provided a `Hashable` instance is in context for that type

of object. `Hashable` instances exist for `String`s, primitive types, sequences of these types, and

product and coproduct types consisting of just other hashable types.



Cryptographic digests have the type `Digest[A]` where `A` is the algorithm type.



For example,

```scala

val digest: Digest[Sha2[384]] = (10, "alpha", 'z').digest[Sha2[384]]

```



### HMACs



Any value whose type has a corresponding `ByteCodec` instance in context may have an HMAC value

calculated, of type `Hmac[A]` (where `A` is the cryptographic algorithm). As a parameter, this

needs an `IArray[Byte]` representing (in some form) the key to be used.



Here is an example using SHA-512:

```scala

val hmac: Hmac[Sha2[512]] = "Hello world".hmac("secret".bytes)

```



### Type inference



Whenever an expression is used in a position with an expected type, the type parameters of the

methods `decrypt`, `digest` and `hmac` may be omitted, for example given the case class,

```scala

case class Block(digest: Digest[Sha2[256]], json: Json, hmac: Hmac[Sha2[512]])

```

we can instantiate it with just,

```scala

val block = Block(data.digest, data.decrypt, value.hmac)

```



Alternatively, a particular given may be imported directly into the current scope to prioritize it,

such that it may be used in preference to the alternatives.



### Byte data



Representations of binary data are common with low-level cryptographic operations. All operations in

Gastronomy use the immutable `IArray[Byte]` type as the underlying representation of binary data,

but typically wrap the data in a type which more precisely indicates the content of that data.



These types include the key types, `PublicKey`, `PrivateKey` and `SymmetricKey`, and result types,

`Signature`, `Hmac`, `Digest` and `Message`.



These types are all further refined with a type parameter representing the cryptographic algorithm

associated with that data. For example, an MD5 digest is typed as, `Digest[Md5]` and a 384-bit SHA-2

HMAC has the type, `Hmac[Sha2[384]]`.



In order to make it easier to share these values, they can be encoded to and from `String`s using

a number of different encodings:

- binary (`Binary`)

- hexadecimal (`Hex`)

- BASE-64 (`Base64`)

- URL-safe BASE-64 (`Base64Url`)



The `encode` method, which exists as an extension on `IArray[Byte]`, as well as (directly) on all

types representing byte data. It takes one of these as a type parameter to produce a `String` of

that data, encoded with the specified encoding.



#### Algorithms



Gastronomy's cryptographic functions are implemented through different algorithms, which are

represented by types. Their names follow the conventions of other Scala types, hence:

- [`Rsa[B]`](https://en.wikipedia.org/wiki/RSA_(cryptosystem)) for `B` of `1024` or `2048`,

- [`Dsa[B]`](https://en.wikipedia.org/wiki/RSA_(cryptosystem)) for `B` of `512`, `1024`, `2048` or

  `3072`,

- [`Aes[B]`](https://en.wikipedia.org/wiki/Advanced_Encryption_Standard) for `B` of `128`, `192` or

  `256`,

- [`Sha1`](https://en.wikipedia.org/wiki/SHA-1),

- [`Sha2[B]`](https://en.wikipedia.org/wiki/SHA-2) for `B` of `224`, `256`, `384` or `512`, and

- [`Md5`](https://en.wikipedia.org/wiki/MD5)



Additionally, the types `Base64`, `Base64Url`, `Hex` and `Binary` represent non-cryptographic

byte-to-string encodings.



### Generating keys



The `PrivateKey` object provides the `generate[A]()` method, where `A` is `Rsa[B]`, `Dsa[B]` or

`Aes[B]` for an appropriate choice of `B`.



The algorithm `Aes[B]` can also be used with the `SymmetricKey` object to get a symmetric key which

has the functionality of both a public and private key.



### Byte codecs



Any object which can be serialized to bytes may be digested, signed, verified, HMACked or encrypted,

and can be returned from a decryption operation, provided a corresponding `ByteCodec` instance is

available for that type.



`ByteCodec`s are provided for `IArray[Byte]` (trivially) and for `String`s (assuming a UTF-8

encoding).



### PEM encoding



The _Privacy-Enhanced Mail_ format is commonly used for exchanging cryptographic values safely in

ASCII-only environments.



A `Pem` type is provided for reading, writing and representing this data. The case class `Pem` has

two fields: `kind`, which is the label that appears after the words `BEGIN` and `END` in the

serialized format, and `data`, which is an `IArray[Byte]` of the byte data.



The `serialize` method will produce a `String` of the data, properly encoded as BASE-64, and

delimited.



The method `Pem.parse` will attempt to parse a `String` containing PEM-encoded data.



All Gastronomy's key types offer a `pem` method which will return an appropriately-labelled `Pem`

value containing that key, however to avoid the risk of accidentally exposing a private key, the

`pem` method of `PrivateKey` must be called with a special singleton value, like so:



```scala

privateKey.pem(RevealSecretKey)

```



### Other Cryptographic Algorithms



Gastronomy may be easily extended to support other cryptographic algorithms. The existing

implementations of `Rsa`, `Dsa`, `Aes`, `Sha1`, `Sha2` and `Md5` should be studied to investigate

this possibility.



## Status



Gastronomy is classified as __fledgling__. For reference, Soundness projects are

categorized into one of the following five stability levels:



- _embryonic_: for experimental or demonstrative purposes only, without any guarantees of longevity

- _fledgling_: of proven utility, seeking contributions, but liable to significant redesigns

- _maturescent_: major design decisions broady settled, seeking probatory adoption and refinement

- _dependable_: production-ready, subject to controlled ongoing maintenance and enhancement; tagged as version `1.0.0` or later

- _adamantine_: proven, reliable and production-ready, with no further breaking changes ever anticipated



Projects at any stability level, even _embryonic_ projects, can still be used,

as long as caution is taken to avoid a mismatch between the project's stability

level and the required stability and maintainability of your own project.



Gastronomy is designed to be _small_. Its entire source code currently consists

of 276 lines of code.



## Building



Gastronomy will ultimately be built by Fury, when it is published. In the

meantime, two possibilities are offered, however they are acknowledged to be

fragile, inadequately tested, and unsuitable for anything more than

experimentation. They are provided only for the necessity of providing _some_

answer to the question, "how can I try Gastronomy?".



1. *Copy the sources into your own project*

   

   Read the `fury` file in the repository root to understand Gastronomy's build

   structure, dependencies and source location; the file format should be short

   and quite intuitive. Copy the sources into a source directory in your own

   project, then repeat (recursively) for each of the dependencies.



   The sources are compiled against the latest nightly release of Scala 3.

   There should be no problem to compile the project together with all of its

   dependencies in a single compilation.



2. *Build with [Wrath](https://github.com/propensive/wrath/)*



   Wrath is a bootstrapping script for building Gastronomy and other projects in

   the absence of a fully-featured build tool. It is designed to read the `fury`

   file in the project directory, and produce a collection of JAR files which can

   be added to a classpath, by compiling the project and all of its dependencies,

   including the Scala compiler itself.

   

   Download the latest version of

   [`wrath`](https://github.com/propensive/wrath/releases/latest), make it

   executable, and add it to your path, for example by copying it to

   `/usr/local/bin/`.



   Clone this repository inside an empty directory, so that the build can

   safely make clones of repositories it depends on as _peers_ of `gastronomy`.

   Run `wrath -F` in the repository root. This will download and compile the

   latest version of Scala, as well as all of Gastronomy's dependencies.



   If the build was successful, the compiled JAR files can be found in the

   `.wrath/dist` directory.



## Contributing



Contributors to Gastronomy are welcome and encouraged. New contributors may like

to look for issues marked

[beginner](https://github.com/propensive/gastronomy/labels/beginner).



We suggest that all contributors read the [Contributing

Guide](/contributing.md) to make the process of contributing to Gastronomy

easier.



Please __do not__ contact project maintainers privately with questions unless

there is a good reason to keep them private. While it can be tempting to

repsond to such questions, private answers cannot be shared with a wider

audience, and it can result in duplication of effort.



## Author



Gastronomy was designed and developed by Jon Pretty, and commercial support and

training on all aspects of Scala 3 is available from [Propensive

OÜ](https://propensive.com/).



## Name



Gastronomy is named after the art and science of "good eating", which leads to digestion, since the library consumes data to produce digests (but has subsequently grown in scope).



In general, Soundness project names are always chosen with some rationale,

however it is usually frivolous. Each name is chosen for more for its

_uniqueness_ and _intrigue_ than its concision or catchiness, and there is no

bias towards names with positive or "nice" meanings—since many of the libraries

perform some quite unpleasant tasks.



Names should be English words, though many are obscure or archaic, and it

should be noted how willingly English adopts foreign words. Names are generally

of Greek or Latin origin, and have often arrived in English via a romance

language.



## Logo



The logo shows a slice of avocado, a gastronomic delight.



## License



Gastronomy is copyright © 2025 Jon Pretty & Propensive OÜ, and

is made available under the [Apache 2.0 License](/license.md).