> For the complete documentation index, see [llms.txt](https://quantumphp.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://quantumphp.gitbook.io/docs/packages/encryption/contracts.md).

# Contracts

The package has one explicit interface and a few code-level behavioral contracts that matter in practice.

## `EncryptionInterface`

`Quantum\Encryption\Contracts\EncryptionInterface` defines two methods:

* `encrypt(string $plain): string`
* `decrypt(string $encrypted): string`

Any adapter used by `Cryptor` must implement both.

## `Cryptor` forwarding contract

`Quantum\Encryption\Cryptor` is not an encryption implementation by itself. It is a delegating wrapper around one adapter.

Current behavior:

* `getAdapter()` returns the exact adapter instance it wraps
* `isAsymmetric()` returns `true` only when the adapter is an `AsymmetricEncryptionAdapter`
* `__call()` forwards method calls only if the adapter actually defines the method

So the package contract is adapter-shaped, even when consumers interact with `Cryptor`.

## Factory contract

`CryptorFactory::resolve($type)` memoizes one `Cryptor` instance per type string on the factory object.

This means the package contract is not "new instance every call". It is "shared cryptor per type per factory instance".

Because `CryptorFactory::get()` itself resolves the factory through `Di::get(...)`, the effective contract becomes:

* one shared factory per DI container
* one shared cryptor per type inside that factory

## Error contract

The package raises a mix of package-specific and shared exceptions.

Common cases:

* unsupported type -> `CryptorException::adapterNotSupported(...)`
* unsupported forwarded method -> `CryptorException::methodNotSupported(...)`
* missing app key in symmetric mode -> `AppException::missingAppKey()`
* invalid symmetric cipher payload -> `CryptorException::invalidCipher()`
* missing asymmetric key properties -> `CryptorException::publicKeyNotProvided()` or `privateKeyNotProvided()`
* OpenSSL key generation/config failure -> `CryptorException::missingConfig('openssl.cnf')`

Asymmetric encrypt/decrypt calls have a looser failure contract after construction. The adapter does not wrap failed `openssl_public_encrypt(...)` or `openssl_private_decrypt(...)` calls, so oversized plaintext or invalid ciphertext can escape as native PHP/OpenSSL errors instead of `CryptorException`.

## Serialization contract in helpers

The package helpers add another contract above the raw adapters:

* `crypto_encode($data, ...)` always serializes the input before encrypting it
* `crypto_decode($encrypted, ...)` decrypts first, then attempts `@unserialize(...)`

If `unserialize(...)` returns anything other than `false`, that value is returned.

If `unserialize(...)` returns `false`, the helper falls back to the decrypted string.

Important edge case:

```php
$value = false;
$encoded = crypto_encode($value);
$decoded = crypto_decode($encoded);
```

`serialize(false)` becomes `b:0;`, and `unserialize('b:0;')` returns `false`. Because the helper uses `!== false` as its success check, this round trip returns the string `b:0;` instead of boolean `false`.


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