Class: Miscreant::STREAM::Decryptor

Inherits:

Object

• Object
• Miscreant::STREAM::Decryptor

Defined in:

lib/miscreant/stream.rb

Overview

A STREAM decryptor

This corresponds to the ???? stream decryptor object as defined in the paper Online Authenticated-Encryption and its Nonce-Reuse Misuse-Resistance

Instance Method Summary

• #initialize(alg, key, nonce) ⇒ Decryptor constructor

  Create a new STREAM decryptor.

• #inspect ⇒ String

  Inspect this STREAM encryptor instance.

• #open(ciphertext, ad: "", last_block: false) ⇒ String

  Decrypt the next message in the stream.

Constructor Details

#initialize(alg, key, nonce) ⇒ Decryptor

Create a new STREAM decryptor.

Parameters:

• alg ("AES-SIV", "AES-PMAC-SIV") —

  cryptographic algorithm to use

• key (String) —

  32-byte or 64-byte random Encoding::BINARY secret key

• nonce (String) —

  8-byte nonce

Raises:

• (TypeError) —

  nonce is not a String

• (ArgumentError) —

  nonce is wrong length or not Encoding::BINARY

# File 'lib/miscreant/stream.rb', line 73

def initialize(alg, key, nonce)
  @aead = AEAD.new(alg, key)
  @nonce_encoder = NonceEncoder.new(nonce)
end

Instance Method Details

#inspect ⇒ String

Inspect this STREAM encryptor instance

Returns:

• (String) —

  description of this instance

# File 'lib/miscreant/stream.rb', line 93

def inspect
  to_s
end

#open(ciphertext, ad: "", last_block: false) ⇒ String

Decrypt the next message in the stream

Parameters:

• ciphertext (String) —

  cipher message to encrypt

• ad (String) (defaults to: "") —

  (optional) associated data to authenticate

• last_block (true, false) (defaults to: false) —

  is this the last block in the STREAM?

Returns:

• (String) —

  plaintext message

Raises:

• (Miscreant::IntegrityError) —

  ciphertext and/or associated data are corrupt or tampered with

# File 'lib/miscreant/stream.rb', line 86

def open(ciphertext, ad: "", last_block: false)
  @aead.open(ciphertext, nonce: @nonce_encoder.next(last_block), ad: ad)
end