Module ECDH
Elliptic Curve DiffieHellman encryption (ECDH)
Asymmetric public/private key encryption technologies.
ECDH encryption and ECDSA signing functionalities are provided by this module. New keyring instances are instantiated by calling the new() method, keys can be imported using the
Alice = ECDH.new()
Bob = 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 20172019
 License: AGPLv3
 Author: Denis "Jaromil" Roio
Global ECDH functions
new (curve)  Create a new ECDH encryption keyring using a specified curve ('BLS383' by default). 
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:public (key)  Imports a public key inside an ECDH keyring. 
keyring:public ()  Returns X and Y coordinates of the public key inside an ECDH keyring. 
keyring:private (key)  Imports a private key inside an ECDH keyring. 
keyring:sign (message)  Elliptic Curve Digital Signature Algorithm (ECDSA) signing function. 
keyring:verify (message, signature)  Elliptic Curve Digital Signature Algorithm (ECDSA) verification function. 
keyring:encrypt (keyring, message, header)  Simple method for AESGCM encryption with Additional Data (AEAD), compatible with IEEE P802.1 specification. 
keyring:ciphertext  Results of keyring:encrypt 
keyring:decrypt (ciphertext)  Simple method for AESGCM decrypt with Additional Data (AEAD). 
keyring:hmac (key, data)  Compute the HMAC of a message using a key. 
keyring:kdf2 (hash, key)  Key Derivation Function (KDF2). 
keyring:pbkdf2 (key, salt, iterations, length)  Password Based Key Derivation Function (PBKDF2). 
Global ECDH functions
 new (curve)

Create a new ECDH encryption keyring using a specified curve
('BLS383' by default).
A keyring object will be returned implementing ECDH methods.
Supported curves: 'BLS383', 'ED25519', 'GOLDILOCKS', 'SECP256K1' (curve)
Parameters:
 curve [opt=BLS383] name of elliptic curve to use
Returns:

a new keyring
Usage:
keyring = ECDH.new()  generate a keypair keypair = keyring:keygen() I.print(keypair) [[{ public = oct[] .... , private = oct[] .... }]]
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. ()
Returns:
 OCTET public key
 OCTET private key
 keyring:public (key)

Imports a public key inside an ECDH keyring.
This is a get/set method working both ways: without argument it returns the public key of a keyring, or if an OCTET argument is provided and is a valid public key it is imported.
If the keyring has a public key already, it will refuse to overwrite it and return an error. (key)
Parameters:
 key [opt] octet of a public key to be imported
 keyring:public ()

Returns X and Y coordinates of the public key inside an ECDH keyring. (key)
Returns:
 OCTET coordinate X of public key
 OCTET coordinate Y of public key
 keyring:private (key)

Imports a private key inside an ECDH keyring.
This is a get/set method working both ways: without argument it returns the private key of a keyring, or if an OCTET argument is provided it is imported as private key inside the keyring and used to derivate its corresponding public key.
If the keyring contains already any key, it will refuse to overwrite them and return an error. (key)
Parameters:
 key [opt] octet of a private key to be imported
 keyring:sign (message)

Elliptic Curve Digital Signature Algorithm (ECDSA) signing
function. This method uses the private key inside a keyring to sign
a message, returning a signature to be used in keyring:verify.
(message)
Parameters:
 message string or OCTET message to sign
Returns:

table containing signature parameters octets (r,s)
Usage:
ecdh = ECDH.keygen()  generate keys or import them m = "Message to be signed" signature = ecdh:sign(m) assert( ecdh:verify(m,signature) )
 keyring:verify (message, signature)

Elliptic Curve Digital Signature Algorithm (ECDSA) verification
function. This method uses the public key iside a keyring to verify
a message, returning true or false. The signature parameters are
returned as 'r' and 's' in this same order by keyring:sign.
(message,signature)
Parameters:
 message the message whose signature has to be verified
 signature the signature table returned by keyring:sign
Returns:

true if the signature is OK, or false if not.
See also:
 keyring:encrypt (keyring, message, header)

Simple method for AESGCM encryption with Additional Data (AEAD),
compatible with IEEE P802.1 specification. Takes a keyring object
for the public key and a table of parameters. Returns also a table
with the cyphertext and a checksum that is accepted by decrypt.
(keyring, message, header)
Parameters:
 keyring recipient keyring containing the public key
 message octet input text to be encrypted for secrecy
 header octet input header authenticated for integrity
Returns:
 keyring:ciphertext

Results of keyring:encrypt
Usage:
{ text = "encrypted text",  OCTET checksum = "control checksum",  OCTET of 16 bytes iv = "random IV",  OCTET of 16 bytes header = "clear text header",  OCTET often encoded JSON table
 keyring:decrypt (ciphertext)

Simple method for AESGCM decrypt with Additional Data
(AEAD). Takes a table as returned by keyring:encrypt containing
text, checksum, header, IV and the sender's pubkey. Returns an
octet containing the decrypted message or error if any problem
arises (invalid checksum etc.). Compatible with IEEE P802.1
specification.
(ciphertext)
Parameters:
 ciphertext table with text, checksum, iv, header and pubkey
Returns:

octet containing the decrypted message
 keyring:hmac (key, data)

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)
Parameters:
 key an octet containing the key to compute the HMAC
 data an octet containing the message to compute the HMAC
Returns:

a new octet containing the computed HMAC or false on failure
 keyring:kdf2 (hash, key)

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.
(key)
Parameters:
Returns:

a new octet containing the derived key
 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: