Module ECDH
Elliptic Curve DiffieHellman encryption (ECDH)
Asymmetric public/private key encryption technologies.
ECDH encryption functionalities are provided with all standard functions by this extension. It is possible to create keyring instances using the new() method:
keyring = ECDH.new()
One can create more keyrings in the same script and call them with meaningful variable names to help making code more understandable. Each keyring instance offers methods prefixed with a doublecolon that operate on arguments as well keys contained by the keyring: this way scripting can focus on the identities represented by each keyring, giving them names as 'Alice' or 'Bob'.
Info:
 Copyright: Dyne.org foundation 20172018
 License: GPLv3
 Author: Denis "Jaromil" Roio, Enrico Zimuel
Global ECDH functions
new (curve) 
Create a new ECDH encryption keyring using a specified curve or

Class keyring
keyring:keygen ()  Generate an ECDH public/private key pair for a keyring
Keys generated are both returned and stored inside the keyring. 
keyring:checkpub (key)  Validate an ECDH public key. 
keyring:session (keyring)  Generate a DiffieHellman shared session key. 
keyring:public (key)  Imports or exports the public key from an ECDH keyring. 
keyring:private (key)  Imports or exports the private key from an ECDH keyring. 
keyring:encrypt_weak_aes_cbc (key, message)  AES encrypts a plaintext to a ciphtertext. 
keyring:decrypt_weak_aes_cbc (key, ciphertext)  AES decrypts a plaintext to a ciphtertext. 
keyring:encrypt (key, message, iv, header)  AESGCM encrypt with Additional Data (AEAD) encrypts and authenticate a plaintext to a ciphtertext. 
keyring:decrypt (key, message, iv, header)  AESGCM decrypt with Additional Data (AEAD) decrypts and authenticate a plaintext to a ciphtertext . 
keyring:hash (string)  Hash an octet into a new octet. 
keyring:hmac (key, data, len)  Compute the HMAC of a message using a key. 
keyring:kdf2 (parameters, key, length)  Key Derivation Function (KDF2). 
keyring:pbkdf2 (key, salt, iterations, length)  Password Based Key Derivation Function (PBKDF2). 
keyring:random (int)  Cryptographically Secure Random Number Generator (RNG). 
Global ECDH functions
 new (curve)

Create a new ECDH encryption keyring using a specified curve or
ED25519 by default if omitted. The ECDH keyring created will offer methods to interact with other keyrings. Supported curves: ed25519, nist256, bn254cx, fp256bn
(curve)
Parameters:
 curve [opt=ed25519] elliptic curve to be used
Returns:

a new ECDH keyring
Usage:
keyring = ECDH.new('ed25519')  generate a keypair keyring:keygen()
Class keyring
Instance Methods keyring:keygen ()

Generate an ECDH public/private key pair for a keyring
Keys generated are both returned and stored inside the keyring. They can also be retrieved later using the
:public()
and:private()
methods if necessary. ()Returns:
 OCTET public key
 OCTET private key
 keyring:checkpub (key)

Validate an ECDH public key. Any octet can be a private key, but
public keys aren't random and checking them is the only validation
possible.
(key)
Parameters:
 key the input public key octet to be validated
Returns:

true if public key is OK, or false if not.
 keyring:session (keyring)

Generate a DiffieHellman shared session key. This function uses
two keyrings to calculate a shared key, then process it through
KDF2 to make it ready for use in keyring:encrypt. This is
compliant with the IEEE1363 DiffieHellman shared secret
specification for asymmetric key encryption.
(keyring)
Parameters:
 keyring containing the public key to be used
Returns:
 octet KDF2 hashed session key ready for keyring:encrypt
 octet a big number result of mod(private,curve_order)*public
See also:
 keyring:public (key)

Imports or exports the public key from an ECDH keyring. This method
functions in two ways: without argument it returns the public key
of a keyring, or if an octet argument is provided it imports it as
public key inside the keyring, but it refuses to overwrite and
returns an error if a public key is already present.
(key)
Parameters:
 key [opt] octet of a public key to be imported
 keyring:private (key)

Imports or exports the private key from an ECDH keyring. This method
functions in two ways: without argument it returns the private key
of a keyring, or if an octet argument is provided it imports it as
private key inside the keyring and generates a public key for it. If
a private key is already present in the keyring it refuses to
overwrite and returns an error.
(key)
Parameters:
 key [opt] octet of a private key to be imported
 keyring:encrypt_weak_aes_cbc (key, message)

AES encrypts a plaintext to a ciphtertext. Function compatible with
IEEE1363
AES_CBC_IV0_ENCRYPT
. Encrypts in CBC mode with a zero IV, pads necessary to create a full final block. This is weak encryption and keyring:encrypt should be preferred. (key, message)Parameters:
 key AES key octet
 message input text in an octet
Returns:

a new octet containing the output ciphertext
 keyring:decrypt_weak_aes_cbc (key, ciphertext)

AES decrypts a plaintext to a ciphtertext. Function compabible
with IEEE1363 specification for AES CBC using IV set to
zero. Decrypts a secret produced using
keyring:encrypt_weak_aes_cbc in CBC mode.
(key, ciphertext)
Parameters:
 key AES key octet
 ciphertext input ciphertext octet
Returns:

a new octet containing the decrypted plain text, or false when failed
 keyring:encrypt (key, message, iv, header)

AESGCM encrypt with Additional Data (AEAD) encrypts and
authenticate a plaintext to a ciphtertext. Function compatible with
IEEE P802.1 specification. Errors out if encryption fails or
authentication fails, else returns the secret ciphertext and a
SHA256 of the header to checksum the integrity of the accompanying
plaintext.
(key, message, iv, h)
Parameters:
 key AES key octet
 message input text in an octet
 iv initialization vector
 header clear text, authenticated for integrity (checksum)
Returns:
 octet containing the output ciphertext
 octet containing the authentication tag (checksum)
 keyring:decrypt (key, message, iv, header)

AESGCM decrypt with Additional Data (AEAD) decrypts and
authenticate a plaintext to a ciphtertext . Compatible with IEEE
P802.1 specification.
(key, ciphertext, iv, h, tag)
Parameters:
 key AES key octet
 message input text in an octet
 iv initialization vector
 header the additional data
Returns:

a new octet containing the output ciphertext and the checksum
 keyring:hash (string)

Hash an octet into a new octet. Use the keyring's hash function to
hash an octet string and return a new one containing the hash of
the string.
(string)
Parameters:
 string octet containing the data to be hashed
Returns:

a new octet containing the hash of the data
 keyring:hmac (key, data, len)

Compute the HMAC of a message using a key. This method takes any
data and any key material to comput an HMAC of the same length of
the hash bytes of the keyring.
(key, data, len)
Parameters:
 key an octet containing the key to compute the HMAC
 data an octet containing the message to compute the HMAC
 len [opt=keyring>hash bytes] length of HMAC or default
Returns:

a new octet containing the computer HMAC or false on failure
 keyring:kdf2 (parameters, key, length)

Key Derivation Function (KDF2). Key derivation is used to
strengthen keys against bruteforcing: they impose a number of
costly computations to be iterated on the key. This function
generates a new key from an existing key applying an octet of key
derivation parameters.
(parameters, key, length)
Parameters:
 parameters
[opt=nil] octet of key derivation parameters (can be
nil
)  key octet of the key to be transformed
 length [opt=key length] integer indicating the new length (default same as input key)
Returns:

a new octet containing the derived key
 parameters
[opt=nil] octet of key derivation parameters (can be
 keyring:pbkdf2 (key, salt, iterations, length)

Password Based Key Derivation Function (PBKDF2). This function
generates a new key from an existing key applying a salt and number
of iterations.
(key, salt, iterations, length)
Parameters:
 key octet of the key to be transformed
 salt octet containing a salt to be used in transformation
 iterations [opt=1000] number of iterations to be applied
 length [opt=key length] integer indicating the new length (default same as input key)
Returns:

a new octet containing the derived key
See also:
 keyring:random (int)

Cryptographically Secure Random Number Generator (RNG).
Returns a new octet filled with random bytes.
This method is initialised with a different seed for each keyring upon creation. It doesn't make any difference to use one keyring's RNG or another, but mixing them and making this behavior specific to different scripts helps randomness.
Cryptographic security is achieved by hashing the random numbers using this sequence: unguessable seed > SHA > PRNG internal state > SHA > random numbers. See this paper for a justification. (int)
Parameters:
 int [opt=rsa>max] length of random material in bytes, defaults to maximum RSA size
Usage:
ecdh = require'ecdh' ed25519 = ecdh.new('ed25519')  generate a random octet (will be sized 2048/8 bytes) csrand = ed25519:random()  print out the cryptographically secure random sequence in hex print(csrand:hex())