Fresco + Conceal, Image Loading with encrypted cache

CryptoFileCache.kt

import com.facebook.binaryresource.BinaryResource
import com.facebook.cache.common.CacheKey
import com.facebook.cache.common.WriterCallback
import com.facebook.cache.disk.FileCache
import com.facebook.crypto.Crypto
import com.facebook.crypto.Entity
import java.io.InputStream

fun configureFresco() {
    val frescoConfig = ImagePipelineConfig.newBuilder(context)
            //... your configuration
            .setFileCacheFactory { diskCacheConfig ->
                val defaultFactory = DiskStorageCacheFactory(DynamicDefaultDiskStorageFactory())
                CryptoFileCache(crypto, defaultFactory.get(diskCacheConfig))
            }
            .build() 
    Fresco.initialize(context, frescoConfig)
}

class CryptoFileCache(val crypto: Crypto, val delegate: FileCache) : FileCache by delegate {

    override fun insert(key: CacheKey, realWriter: WriterCallback): BinaryResource {
        return delegate.insert(key) { outputStream ->
            val cipherOutputStream = crypto.getCipherOutputStream(outputStream, Entity.create(key.uriString))
            realWriter.write(cipherOutputStream)

            //This is important, the delegate will only flush / close the incoming stream
            cipherOutputStream.flush()
            cipherOutputStream.close()
        }
    }

    override fun getResource(key: CacheKey): BinaryResource? {
        val encryptedResource = delegate.getResource(key) ?: return null
        return object : BinaryResource {
            //This size will be ~30 bytes off depending on Conceal algorithm (version + cypher + IV)
            override fun size(): Long = encryptedResource.size()

            override fun openStream(): InputStream {
                return crypto.getCipherInputStream(encryptedResource.openStream(), Entity.create(key.uriString))
            }

            override fun read(): ByteArray {
                return crypto.decrypt(encryptedResource.read(), Entity.create(key.uriString))
            }
        }
    }
}