.. index:: single: ed25519
.. _ed25519/0:

.. rst-class:: right

**category**

``ed25519``
===========

Ed25519 (RFC 8032) public-key signature implementation. Requires exact, unbounded integer arithmetic for arithmetic modulo the 255-bit field prime and modulo the group order.

| **Availability:** 
|    ``logtalk_load(crypto(loader))``

| **Author:** Paulo Moura
| **Version:** 1:0:0
| **Date:** 2026-08-02

| **Compilation flags:**
|    ``static``


| **Complements:**
|    :ref:`crypto <crypto/0>`
| **Uses:**
|    :ref:`list <list/0>`
|    :ref:`sha512 <sha512/0>`
|    :ref:`type <type/0>`

| **Remarks:**
|    (none)

| **Inherited public predicates:**
|    (none)

.. contents::
   :local:
   :backlinks: top

Public predicates
-----------------

.. index:: ed25519_keypair/2
.. _ed25519/0::ed25519_keypair/2:

``ed25519_keypair/2``
^^^^^^^^^^^^^^^^^^^^^

Generates a fresh random 32-byte Seed and derives the corresponding 32-byte PublicKey. The seed is the value to keep secret and to pass to ed25519_sign/3; it is also sometimes called the "secret key". Available only on backends with unbounded integer arithmetic.

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``ed25519_keypair(Seed,PublicKey)``
| **Mode and number of proofs:**
|    ``ed25519_keypair(-list(byte),-list(byte))`` - ``one``


------------

.. index:: ed25519_public_key/2
.. _ed25519/0::ed25519_public_key/2:

``ed25519_public_key/2``
^^^^^^^^^^^^^^^^^^^^^^^^

Derives the 32-byte PublicKey corresponding to a 32-byte Seed. Available only on backends with unbounded integer arithmetic.

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``ed25519_public_key(Seed,PublicKey)``
| **Mode and number of proofs:**
|    ``ed25519_public_key(+list(byte),-list(byte))`` - ``one_or_error``

| **Exceptions:**
|    ``Seed`` is a partial list or a list with an element which is a variable:
|        ``instantiation_error``
|    ``Seed`` is neither a variable nor a list of 32 bytes:
|        ``type_error(list(byte,32),Seed)``
|    ``Seed`` contains a non-integer byte:
|        ``type_error(integer,Byte)``
|    ``Seed`` contains an integer outside the byte range:
|        ``domain_error(byte,Byte)``


------------

.. index:: ed25519_sign/3
.. _ed25519/0::ed25519_sign/3:

``ed25519_sign/3``
^^^^^^^^^^^^^^^^^^

Computes the 64-byte Ed25519 Signature of Message using Seed. Not constant-time; see the module-level note on this section. Available only on backends with unbounded integer arithmetic.

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``ed25519_sign(Seed,Message,Signature)``
| **Mode and number of proofs:**
|    ``ed25519_sign(+list(byte),+list(byte),-list(byte))`` - ``one_or_error``

| **Exceptions:**
|    ``Seed`` is a partial list or a list with an element which is a variable:
|        ``instantiation_error``
|    ``Seed`` is neither a variable nor a list of 32 bytes:
|        ``type_error(list(byte,32),Seed)``
|    ``Seed`` contains a non-integer byte:
|        ``type_error(integer,Byte)``
|    ``Seed`` contains an integer outside the byte range:
|        ``domain_error(byte,Byte)``
|    ``Message`` is a partial list or a list with an element which is a variable:
|        ``instantiation_error``
|    ``Message`` is neither a variable nor a list of bytes:
|        ``type_error(list(byte),Message)``
|    ``Message`` contains a non-integer byte:
|        ``type_error(integer,Byte)``
|    ``Message`` contains an integer outside the byte range:
|        ``domain_error(byte,Byte)``


------------

.. index:: ed25519_verify/3
.. _ed25519/0::ed25519_verify/3:

``ed25519_verify/3``
^^^^^^^^^^^^^^^^^^^^

Succeeds if Signature is a valid Ed25519 signature of Message under PublicKey, and fails otherwise (invalid signature, non-canonical S, non-canonical or small-order PublicKey or R component, or malformed input lengths); see the module-level note on this section for the exact verification policy. Available only on backends with unbounded integer arithmetic.

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``ed25519_verify(PublicKey,Message,Signature)``
| **Mode and number of proofs:**
|    ``ed25519_verify(+list(byte),+list(byte),+list(byte))`` - ``zero_or_one``


------------

Protected predicates
--------------------

(no local declarations; see entity ancestors if any)

Private predicates
------------------

(no local declarations; see entity ancestors if any)

Operators
---------

(none)