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59 lines
3.4 KiB
Plaintext
59 lines
3.4 KiB
Plaintext
Draft proposal for how crypto will be implemented.
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Encryption library used: http://nacl.cr.yp.to/
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When running the program for the first time the crypto_box_keypair() function is used to
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generate the users public-private key pair. (32 bytes each)
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The generated public key is set as the client_id of the peer.
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Adding a friend:
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Alice adds bob to her friends list by adding his 32 byte public key (client_id) to her friends list.
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2 cases:
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case 1: Alice adds Bobs public key and bob waits for Alice to attempt to connect to him.
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case 2: Bob and Alice add their respective public keys to their friends list at the same time.
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case 1:
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Alice connects to Bob and sends a data packet (friends request) like so:
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[char with a value of 01][Alice's Public key (client_id) (32 bytes)][Random nonce (24 bytes)][Encrypted message]
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Where the encrypted message is encrypted with crypto_box() (using Bobs public key, Alice's private key
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and the nonce (randomly generated 24 bytes)) and is a message from Alice in which she tells Bob who she is.
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Ex: hello bob it's me alice -_- add me pl0x.
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Bob receives the request and decrypts the message using the function crypto_box_open()
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If the message decrypts successfully:
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If Alice is already in Bobs friends list: case 2
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If Alice is not in Bob's friends list: Bob is prompt to add Alice and is shown the message from her.
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If Bobs accepts Alice's friends request he adds her public key to his friends list.
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case 2:
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Bob and Alice both have the others public key in their friends list, they are ready for the next step: Connecting to an already added friend
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In the next step.
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only crypto_box() is used for encryption and only crypto_box_open() for decryption (just like in the last step.)
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Connecting to an already added friend:
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Alice and Bob are friends.
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As soon as they connect they each generate a new keypair which will only be used for the current connection (The session keys).
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They then send themselves the following packet (the crypto handshake) (encrypted part encrypted with the public nonce in the packet
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the public key of the receiver and private key of the sender)
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[char with a value of 02][Senders Public key (client_id) (32 bytes)][Random nonce (24 bytes)][Encrypted message containing: [random 24 bytes base nonce][session public key of the peer (32 bytes)]]
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If the packet is decrypted successfully:
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Each start using the secret nonce, the public key provided by the other and their own session private key to encrypt data packets (adding to it + 1 for each packet.)
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Each node sends themselves an empty data packet (data packet with 4 encrypted zero bytes)
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Data packet:
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[char with a value of 03][Encrypted data]
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Each data packet received it is decrypted using the secret nonce sent to the other(with +1 added for the first packet +2 for the second, etc...)
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along with the private session key of the receiver.
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Every data packet sent is encrypted using the secret nonce we received (with +1 added for the first packet +2 for the second, etc...),
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the session public key of the receiver and the session private key of the sender.
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The encrypted connection is only deemed successful when the empty data packet is received and decrypted successfully.
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