Storage

The Flow Wallet Kit for Android implements a secure and efficient storage system for managing wallet data and user preferences.

Overview

The storage system is built on top of Android's security best practices, utilizing:

Android Keystore System for cryptographic key storage
EncryptedSharedPreferences for secure data persistence
Room database for structured data storage
File-based encryption for larger data sets

Usage

Basic Storage Operations

import io.outblock.flowwalletkit.storage.WalletStorage
 
// Initialize storage
val storage = WalletStorage.getInstance(context)
 
// Store data
storage.saveString("key", "value")
storage.saveEncrypted("sensitive_key", "sensitive_value")
 
// Retrieve data
val value = storage.getString("key")
val sensitiveValue = storage.getEncrypted("sensitive_key")
 
// Remove data
storage.remove("key")

Storing Wallet Data

import io.outblock.flowwalletkit.storage.WalletData
 
// Store wallet information
val walletData = WalletData(
    address = "0x1234...",
    publicKey = "abc...",
    encryptedPrivateKey = "encrypted..."
)
storage.saveWallet(walletData)
 
// Retrieve wallet information
val wallet = storage.getWallet()

Security Features

Encryption

All sensitive data is encrypted using:

AES-256 for data encryption
RSA for key encryption
SHA-256 for hashing

Key Protection

Private keys are:

Encrypted before storage
Never stored in plaintext
Protected by Android Keystore
Accessible only by your app

Data Types

The storage system supports various data types:

Strings
Numbers
Boolean values
Binary data
JSON objects
Custom serializable objects

Best Practices

Always encrypt sensitive data
// Do this storage.saveEncrypted("private_key", privateKey) // Don't do this storage.saveString("private_key", privateKey)
Use appropriate storage methods
// For small data storage.saveString("preference", "value") // For structured data storage.saveObject("user", userObject) // For large datasets storage.saveToDatabase(data)
Handle errors appropriately
try { storage.saveEncrypted("key", "value") } catch (e: StorageException) { // Handle storage errors Log.e("Storage", "Failed to save data", e) }

Migration

The storage system supports data migration between versions:

storage.migrate { oldVersion, newVersion ->
    when (oldVersion) {
        1 -> migrateFromV1ToV2()
        2 -> migrateFromV2ToV3()
    }
}

Backup & Recovery

The storage system includes backup and recovery features:

// Create backup
val backup = storage.createBackup()
 
// Restore from backup
storage.restoreFromBackup(backup)

Thread Safety

The storage implementation is thread-safe and can be accessed from multiple threads:

// Safe to use from any thread
coroutineScope.launch {
    storage.saveAsync("key", "value")
}

Error Handling

sealed class StorageError : Exception() {
    class EncryptionError : StorageError()
    class DataNotFound : StorageError()
    class InvalidData : StorageError()
    class StorageUnavailable : StorageError()
}
 
try {
    storage.getEncrypted("key")
} catch (e: StorageError) {
    when (e) {
        is StorageError.DataNotFound -> // Handle missing data
        is StorageError.EncryptionError -> // Handle encryption issues
        is StorageError.InvalidData -> // Handle corrupted data
        is StorageError.StorageUnavailable -> // Handle storage unavailability
    }
}

Storage

On this page