> ## Documentation Index
> Fetch the complete documentation index at: https://docs.prism.byescaleira.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Encryption & Compression

> Transparent AES-GCM encryption and multi-algorithm compression wrappers for any store

## PrismEncryptedStore

Transparent encryption wrapper. Encrypts with AES-GCM before delegating to inner store. Decrypts on load.

```swift theme={null}
import CryptoKit

let key = SymmetricKey(size: .bits256)
let defaults = PrismDefaultsStore()
let secure = PrismEncryptedStore(wrapping: defaults, key: key)

// Values encrypted at rest
try secure.save("api-key-secret", forKey: "apiKey")
let apiKey = try secure.load(String.self, forKey: "apiKey") // decrypted

// Also accepts raw key data
let secure2 = PrismEncryptedStore(wrapping: defaults, keyData: keyData)
```

### Async Variant

```swift theme={null}
let disk = PrismDiskStore(directory: .applicationSupport)
let secureDisk = PrismEncryptedAsyncStore(wrapping: disk, key: key)

try await secureDisk.save(credentials, forKey: "creds")
```

### Security

* **Algorithm**: AES-GCM (authenticated encryption)
* **Nonce**: Auto-generated per encryption
* **Format**: Combined nonce + ciphertext + tag
* Wrong key → `PrismStorageError.decryptionFailed`

## PrismCompressedStore

Transparent compression wrapper. Compresses before save, decompresses on load.

```swift theme={null}
let store = PrismCompressedStore(
    wrapping: PrismDefaultsStore(),
    algorithm: .lzfse // default
)

// Large payloads compressed transparently
let bigPayload = Array(0..<10_000)
try store.save(bigPayload, forKey: "data")
let loaded = try store.load([Int].self, forKey: "data")
```

### Algorithms

| Algorithm | Speed   | Ratio  | Use Case                     |
| --------- | ------- | ------ | ---------------------------- |
| `.lzfse`  | Fast    | Good   | Default — Apple optimized    |
| `.lz4`    | Fastest | Lower  | Real-time, low latency       |
| `.zlib`   | Medium  | Better | Cross-platform compatibility |
| `.lzma`   | Slow    | Best   | Archival, max compression    |

### Async Variant

```swift theme={null}
let compressedDisk = PrismCompressedAsyncStore(
    wrapping: PrismDiskStore(),
    algorithm: .lzma
)
```

## Combining Layers

Stack encryption + compression for maximum efficiency:

```swift theme={null}
let base = PrismDefaultsStore()
let compressed = PrismCompressedStore(wrapping: base, algorithm: .lzfse)
let secure = PrismEncryptedStore(wrapping: compressed, key: key)

// Data flow: value → JSON → compress → encrypt → store
try secure.save(sensitiveData, forKey: "payload")
```

<Tip>
  Compress **before** encrypting. Encrypted data has high entropy and compresses poorly.
</Tip>