DSSS

Decentralized Secure Storage System

System Components

Upload Client

• Reads the Public/Private key pair for encryption.
• Divide, encrypt and upload files.
• Generate and upload the Manifest file.
• Asks the server "Where to upload" queries.

Download Client

• Reads the Public/Private key pair for encryption.
• Fetches the manifest file from its first hash.
• Asks the server "Who Has" queries.
• Download file parts from the Manifest.
• Join parts and decrypt each part.

Discovery Server

• Respond and delegates the "Who Has" queries from the client.
• Respond to "Where to upload" queries from the client.
• Respond to "IntroduceMe" queries from the client.
• Persistent connection with the agents.

Agent

• Persistent connection with the discovery server.
• Respond to "Who Has" from the server.
• Respond to "InroductionRequests" from the server.
• Accept upload/get connections from peers.
• Store the hash/value pair on the FS.

Protocol Definition

• Server/Client communication (HTTP Endpoints)

  • Who Has (GET /api/who-has?q=<hash>)
    • JSON Response { addresses : ["X.X.X.X:Z", "Y.Y.Y.Y:Q"] }
  • Where to upload (GET /api/where-to-upload?size=<size>)
    • The response contain all the replicas to which the client should upload
    • JSON Response { addresses : ["X.X.X.X:Z", "Y.Y.Y.Y:Q"] }
  • Introduce Me (GET /api/introduce-me?to=<address>&hash=<hash>&size=<size>)
    • The response contains the key the client should use to contact the agent
    • JSON Response { introduction-key : "X.X.X.X:Z" }

• Server/Agent PING UPD connection for hole punching.

• Server/Agent communication (Persistent TCP connection)

  • Who has ("WHO_HAS <hash>")
    • Response "(0|1)"
  • Introduction Requests ("INTRODUCTION_REQUEST <address> <size> <hash>")
    • Response ("<Introduction Key>")

• Server/Agent communication (TCP over UDP using hole punching)

  • Upload Requests ("UPLOAD <Introduction Key> <hash> <data>")
    • Response ("Ok")
  • Download Requests ("DOWNLOAD <hash>")
    • Response ("<data>")

Upload Flow

• Divide the file into X KBs parts.
• Encrypt each part and get its hash.
• For Each Part Do :
  • Store the hash into a manifest file.
  • Where to upload request to the discovery service.
  • For each address in the query response Do :
    • Introduction request.
    • Use the key in the response to send an upload request to the peer.
• Dump the manifest File, later ( TODO: Upload the file to the network )

Download Flow

• Read the manifest file ( TODO: Fetch it from the network )
• For Each Line in the manifest Do :
  • Send a who has request.
  • Contact one of the peers, the server sent, with a download request . ( TODO: Authenticate first )
  • Decrypt file.
• Concat all parts and dump it.

Agent Connection Flow

• Opens a TCP connection to the server.
• Receives the "Hi " message from the server.
• Opens a UDP connection with the server and periodically sending "PING " in the background.
• Responds to the queries sent by the server using the TCPReaderWriter package.
• Responds to the special query "PING" by a "PONG", all encoded using the TCPReaderWriter.