https://github.com/spider-gazelle/SPAKE2_plus

a crystal lang implementation of SPAKE2+, a Password Authenticated Key Exchange (PAKE) protocol
https://github.com/spider-gazelle/SPAKE2_plus

Last synced: about 2 months ago
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a crystal lang implementation of SPAKE2+, a Password Authenticated Key Exchange (PAKE) protocol

• Host: GitHub
• URL: https://github.com/spider-gazelle/SPAKE2_plus
• Owner: spider-gazelle
• License: mit
• Created: 2023-10-16T12:58:47.000Z (9 months ago)
• Default Branch: main
• Last Pushed: 2023-10-16T22:13:36.000Z (9 months ago)
• Last Synced: 2024-02-01T15:50:03.146Z (5 months ago)
• Language: Crystal
• Size: 13.7 KB
• Stars: 1
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Lists

• awesome-crystal - SPAKE2+ - Password Authenticated Key Exchange (PAKE) protocol, comparable to SRP-6a (Algorithms and Data structures)

README

        
# SPAKE2+

A crystal lang implementation of SPAKE2+

* see: https://datatracker.ietf.org/doc/pdf/draft-bar-cfrg-spake2plus-02.pdf

This is the specific draft used by Matter protocol

## Installation

1. Add the dependency to your `shard.yml`:

   ```yaml

   dependencies:

     spake2_plus:

       github: spider-gazelle/spake2_plus

   ```

2. Run `shards install`

## Usage

This is a basic overview of how matter protocol performs PAKE

```mermaid

sequenceDiagram

    Initiator->>Responder: PBKDF Param Request

    Responder->>Initiator: PBKDF Response (salt + iterations)

    Initiator->>Responder: PAKE Contribution

    Responder->>Initiator: PAKE Contribution + PAKE Verification

    Initiator->>Responder: PAKE Verification

    Responder->>Initiator: PAKE Finished

```

In code this looks like

```crystal

require "spake2_plus"

# the configuration matter uses

algorithm = SPAKE2Plus::Algorithms.new(:p256, :sha256, :hmac)

# As part of registration we swap salt and iteration params

# PBKDF Param Request

random = Random.new

iterations = random.rand(1000..100_000)

salt = random.random_bytes(random.rand(16..32))

# both initiator and responder encode the password / pin

# for Matter this is a UInt32 passcode encoded in little endian

passcode = 1122334455_u32

io = IO::Memory.new

io.write_bytes(passcode, IO::ByteFormat::LittleEndian)

context = io.to_slice

# > The Initiator provides PAKE Contribution

# ==========================================

w0, w1 = algorithm.compute_w0_w1(context, salt, iterations)

initiator = SPAKE2Plus.new(context, w0, algorithm)

x = initiator.compute_x # send x as pake1 to responder

# < Responder provides PAKE Contribution and verification

# =======================================================

w0, l = algorithm.compute_w0_l(context, salt, iterations)

responder = SPAKE2Plus.new(context, w0, algorithm)

y = responder.compute_y

ke, h_ay, resp_verify = responder.compute_secret_and_verifiers_from_x(l, x, y)

# send y, resp_verify as pake2 to initiator

# > The Initiator verifies and sends verifier

# ===========================================

ke, init_verify, h_bx = initiator.compute_secret_and_verifiers_from_y(w1, x, y)

raise "init verification failed" unless h_bx == resp_verify

# send init_verify as pake3 to responder

# < Responder validates and sends PakeFinished

# ============================================

raise "resp verification failed" unless h_ay == init_verify

puts "success!"

```

## Contributors

* [Stephen von Takach](https://github.com/stakach) - creator and maintainer