Class: Noise::Functions::Cipher::AesGcm

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

Constant Summary collapse

MAX_NONCE = 
2**64 - 1

Instance Method Summary collapse

Instance Method Details

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



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# File 'lib/noise/functions/cipher/aes_gcm.rb', line 19

def decrypt(k, n, ad, ciphertext)
  cipher = OpenSSL::Cipher.new('aes-256-gcm').decrypt
  cipher.key = k
  cipher.iv = nonce_to_bytes(n)
  cipher.auth_data = ad
  cipher.auth_tag = ciphertext[-16..]
  update(cipher, ciphertext[0...-16]) + 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/aes_gcm.rb', line 9

def encrypt(k, n, ad, plaintext)
  cipher = OpenSSL::Cipher.new('aes-256-gcm').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 big-endian 64 bit integer.



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# File 'lib/noise/functions/cipher/aes_gcm.rb', line 31

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 264-1, 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/aes_gcm.rb', line 41

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