Module: Eth::Devp2p::Crypto

Extended by:
Crypto
Included in:
Crypto
Defined in:
lib/ethruby/devp2p/crypto.rb

Defined Under Namespace

Classes: ECIESDecryptionError

Constant Summary collapse

ECIES_CIPHER_NAME = 
'aes-128-ctr'

Instance Method Summary collapse

Instance Method Details

#ecies_decrypt(data, priv_key, shared_mac_data = '') ⇒ Object

Raises:



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# File 'lib/ethruby/devp2p/crypto.rb', line 40

def ecies_decrypt(data, priv_key, shared_mac_data = '')
  raise ECIESDecryptionError.new('invalid header') if data[0] != "\x04"

  # compute shared_secret
  ephem_raw_pubkey = data[1..65]
  ephem_pubkey = ec_pkey_from_raw(ephem_raw_pubkey)
  shared_secret = priv_key.dh_compute_key(ephem_pubkey.public_key)

  key = ecies_kdf(shared_secret, 32)
  key_enc, key_mac = key[0...16], key[16..-1]

  # verify data
  key_mac = Digest::SHA256.digest(key_mac)
  tag = data[-32..-1]
  # should use secure_compare?
  unless hmac_sha256(key_mac, data[66...-32] + shared_mac_data) == tag
    raise ECIESDecryptionError.new("Fail to verify data")
  end

  # decrypt data
  cipher = OpenSSL::Cipher.new(ECIES_CIPHER_NAME)

  iv_start = 66
  iv_end = iv_start + cipher.iv_len
  iv = data[iv_start...iv_end]
  ciphertext = data[iv_end...-32]

  cipher.decrypt
  cipher.key = key_enc
  cipher.iv = iv
  cipher.update(ciphertext) + cipher.final
end

#ecies_encrypt(message, raw_pubkey, shared_mac_data = '') ⇒ Object 



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# File 'lib/ethruby/devp2p/crypto.rb', line 17

def ecies_encrypt(message, raw_pubkey, shared_mac_data = '')
  pubkey = raw_pubkey.is_a?(OpenSSL::PKey::EC) ? raw_pubkey : ec_pkey_from_raw(raw_pubkey)

  # compute keys
  ephem_key = OpenSSL::PKey::EC.new('secp256k1')
  ephem_key.generate_key
  shared_secret = ephem_key.dh_compute_key(pubkey.public_key)
  key = ecies_kdf(shared_secret, 32)
  key_enc, key_mac = key[0...16], key[16..-1]

  key_mac = Digest::SHA256.digest(key_mac)
  ephem_raw_pubkey = ephem_key.public_key.to_bn.to_s(2)

  cipher = OpenSSL::Cipher.new(ECIES_CIPHER_NAME)
  cipher.encrypt
  iv = cipher.random_iv
  cipher.key = key_enc
  cipher_text = cipher.update(message) + cipher.final
  msg = "\x04" + ephem_raw_pubkey + iv + cipher_text
  tag = hmac_sha256(key_mac, msg[(1 + 65)..-1] + shared_mac_data)
  msg + tag
end