多喝酸奶有什么好处

Question

I recently saw the BIP 324 proposal. It shows us there can be some privacy enhancement by using ECDH secrets and encryption algorithms such as ChaCha20 and AEAD-ChaCha20-Poly1305. The proposal includes:

• The length decriptor size is reduced to 3 Bytes.
• The command could be expressed as an ID (1 Byte) OR as characters (13 Bytes, by including the 0x00 byte selector).

1. However, I don't fully understand the order in data will be structured. Can it be explained ?
2. What algorithm will be applied to which data structure ? Because I can suppose the ChaCha20 is used in order to encrypt the payload size and AEAD-ChaCha20-Poly1305 to encrypt payload.

Answer 1

In the new P2P transport protocol proposed in BIP324, after the handshake (which among other things establishes encryption keys), packets have the following structure:

• A 3-byte length descriptor (encrypted with FSChaCha20)
• An arbitrary-length ciphertext which is the encryption of a plaintext (encrypted with FSChaCha20Poly1305, which expands the data by 16 bytes in the process by adding a Poly1305 authentication tag); the plaintext consists of:
  • A 1-byte header (which is used for signalling decoy data)
  • A variable-length contents (whose length is described by the length descriptor). The contents consists of:
    • A 1-byte or 13-byte message type (e.g. version, verack, tx, inv, ...).
    • A variable-length payload (the actual data sent in the message).

So if you want everything flattened out, you get:

• 3-byte encrypted length descriptor
• 1-byte encrypted header
• 1-byte or 13-byte encrypted message type
• variable length encrypted payload
• 16-byte Poly1305 authentication tag

However, only 2 separate encryption algorithm invocations are used per packet:

• The 3-byte length is encrypted using FSChaCha20, which is a variant of the ChaCha20 stream cipher that rekeys every 224 messages.
• The header, message type, and payload are all encrypted together at once using FSChaCha20Poly1305, which is a variant of the ChaCha20Poly1305 AEAD which rekeys every 224 messages.