Class: Noise::Functions::Cipher::ChaChaPoly

Inherits:
Object
  • Object
show all
Defined in:
lib/noise/functions/cipher/cha_cha_poly.rb

Constant Summary collapse

MAX_NONCE = 
2**64 - 1
ALGORITHM =

The name OpenSSL knows the AEAD construction of RFC 8439 by. It takes a 12 byte nonce and produces a 16 byte authentication tag, which is what the Noise specification requires of the ChaChaPoly cipher functions.

'chacha20-poly1305'
TAGLEN =

Length in bytes of the authentication tag that encrypt appends to the ciphertext.

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Instance Method Summary collapse

Instance Method Details

#decrypt(k, n, ad, ciphertext) ⇒ Object 



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# File 'lib/noise/functions/cipher/cha_cha_poly.rb', line 27

def decrypt(k, n, ad, ciphertext)
  cipher = OpenSSL::Cipher.new(ALGORITHM).decrypt
  cipher.key = k
  cipher.iv = nonce_to_bytes(n)
  cipher.auth_data = ad
  cipher.auth_tag = ciphertext[-TAGLEN..]
  update(cipher, ciphertext[0...-TAGLEN]) + cipher.final
rescue OpenSSL::Cipher::CipherError => e
  raise Noise::Exceptions::DecryptError, "Decrpyt failed. #{e.message}", e.backtrace
end

#encrypt(k, n, ad, plaintext) ⇒ Object 



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# File 'lib/noise/functions/cipher/cha_cha_poly.rb', line 17

def encrypt(k, n, ad, plaintext)
  cipher = OpenSSL::Cipher.new(ALGORITHM).encrypt
  cipher.key = k
  cipher.iv = nonce_to_bytes(n)
  cipher.auth_data = ad
  update(cipher, plaintext) + cipher.final + cipher.auth_tag
rescue OpenSSL::Cipher::CipherError => e
  raise Noise::Exceptions::EncryptError, "Encrypt failed. #{e.message}", e.backtrace
end

#nonce_to_bytes(n) ⇒ Object

4 zero bytes followed by n as a little-endian 64 bit integer.



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# File 'lib/noise/functions/cipher/cha_cha_poly.rb', line 39

def nonce_to_bytes(n)
  "\x00" * 4 + [n].pack('Q<')
end

#rekey(k) ⇒ Object

Returns a new 32-byte cipher key as a pseudorandom function of k. If this function is not specifically defined for some set of cipher functions, then it defaults to returning the first 32 bytes from ENCRYPT(k,maxnonce, zerolen, zeros), where maxnonce equals 2**64-1, zerolen is a zero-length byte sequence, and zeros is a sequence of 32 bytes filled with zeros.



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# File 'lib/noise/functions/cipher/cha_cha_poly.rb', line 49

def rekey(k)
  encrypt(k, MAX_NONCE, '', "\x00" * 32)[0...32]
end