### Installation

Source: https://github.com/altcha-org/altcha-wordpress-next/blob/main/vendor/altcha-org/altcha/README.md

Install the ALTCHA PHP library using Composer.

```sh
composer require altcha-org/altcha
```

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

### Usage Example

Source: https://github.com/altcha-org/altcha-wordpress-next/blob/main/vendor/altcha-org/altcha/README.md

Demonstrates how to create, solve, and verify an ALTCHA challenge using the PHP library.

```php
<?php

require 'vendor/autoload.php';

use AltchaOrg\Altcha\Altcha;
use AltchaOrg\Altcha\CreateChallengeOptions;
use AltchaOrg\Altcha\SolveChallengeOptions;
use AltchaOrg\Altcha\VerifySolutionOptions;
use AltchaOrg\Altcha\Payload;
use AltchaOrg\Altcha\Algorithm\Pbkdf2;

$pbkdf2 = new Pbkdf2();
$altcha = new Altcha(
    hmacSignatureSecret: 'secret',
    hmacKeySignatureSecret: 'key-secret', // optional, enables fast verification path
);

// Create a new challenge
// Modify the cost and counter depending on the algorithm
$challenge = $altcha->createChallenge(new CreateChallengeOptions(
    algorithm: $pbkdf2,
    cost: 5000,
    counter: random_int(5000, 10000),
    expiresAt: time() + 600,
));

// Solve the challenge (client-side in production)
$solution = $altcha->solveChallenge(new SolveChallengeOptions(
    algorithm: $pbkdf2,
    challenge: $challenge,
));

// Verify the solution (server-side)
if ($solution !== null) {
    $payload = new Payload($challenge, $solution);
    $result = $altcha->verifySolution(new VerifySolutionOptions(
        algorithm: $pbkdf2,
        payload: $payload,
    ));

    if ($result->verified) {
        echo "Solution verified!\n";
    }
}

```

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

### Scrypt Algorithm Initialization

Source: https://github.com/altcha-org/altcha-wordpress-next/blob/main/vendor/altcha-org/altcha/README.md

Example of initializing the Scrypt algorithm.

```php
use AltchaOrg\Altcha\Algorithm\Scrypt;

new Scrypt();
```

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

### Payload Serialization

Source: https://github.com/altcha-org/altcha-wordpress-next/blob/main/vendor/altcha-org/altcha/README.md

Examples of serializing a Payload object.

```php
$payload = new Payload($challenge, $solution);

$payload->toArray();   // array
$payload->toJson();    // JSON string
$payload->toBase64();  // base64-encoded JSON
```

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

### Verifying Specific Form Fields Hash

Source: https://github.com/altcha-org/altcha-wordpress-next/blob/main/vendor/altcha-org/altcha/README.md

Example of verifying the hash of specific form fields.

```php
$isValid = ServerSignature::verifyFieldsHash(
    formData: ['name' => 'John', 'email' => 'john@example.com'],
    fields: ['name', 'email'],
    fieldsHash: hash('sha256', "John\njohn@example.com"),
);
```

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

### Server Signature Verification

Source: https://github.com/altcha-org/altcha-wordpress-next/blob/main/vendor/altcha-org/altcha/README.md

Example of verifying a server signature payload and accessing verification data.

```php
use AltchaOrg\Altcha\ServerSignature;

$result = ServerSignature::verifyServerSignature($payload, 'server-secret');

if ($result->verified) {
    $result->verificationData->expire;          // int
    $result->verificationData->score;           // float
    $result->verificationData->verified;        // bool
    $result->verificationData->fields;          // array
    $result->verificationData->classification;  // string
    $result->verificationData['email'];         // array access also works
}
```

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

### Running Tests

Source: https://github.com/altcha-org/altcha-wordpress-next/blob/main/vendor/altcha-org/altcha/README.md

Command to run the project's tests.

```sh
vendor/bin/phpunit tests
```

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

### Argon2id Algorithm Initialization

Source: https://github.com/altcha-org/altcha-wordpress-next/blob/main/vendor/altcha-org/altcha/README.md

Instantiate the Argon2id algorithm. Requires ext-sodium.

```php
use AltchaOrg\Altcha\Algorithm\Argon2id;

new Argon2id();
```

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

### Run E2E Tests

Source: https://github.com/altcha-org/altcha-wordpress-next/blob/main/e2e/README.md

Command to execute the End-to-End tests.

```sh
npm test
```

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

### PBKDF2 Algorithm Initialization

Source: https://github.com/altcha-org/altcha-wordpress-next/blob/main/vendor/altcha-org/altcha/README.md

Instantiate the PBKDF2 algorithm with different HMAC algorithms.

```php
use AltchaOrg\Altcha\Algorithm\Pbkdf2;
use AltchaOrg\Altcha\HmacAlgorithm;

new Pbkdf2();                        // PBKDF2/SHA-256
new Pbkdf2(HmacAlgorithm::SHA384);  // PBKDF2/SHA-384
new Pbkdf2(HmacAlgorithm::SHA512);  // PBKDF2/SHA-512
```

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

### Altcha Class Initialization

Source: https://github.com/altcha-org/altcha-wordpress-next/blob/main/vendor/altcha-org/altcha/README.md

Initialize the Altcha class with secret keys and optional HMAC algorithm.

```php
$altcha = new Altcha(
    hmacSignatureSecret: 'secret',
    hmacKeySignatureSecret: 'key-secret', // enables fast verification path
    hmacAlgorithm: HmacAlgorithm::SHA256, // default
);
```

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

### PGP Key for Encrypted Reports

Source: https://github.com/altcha-org/altcha-wordpress-next/blob/main/SECURITY.md

Recommended for encrypting security reports to ensure confidentiality.

```text
https://altcha.org/pgp/security-public-key.asc
```

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