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OpenSats is funding five more open-source projects in the nostr ecosystem.
NIP-44
versioned encryption, NIP-44 v2, Nostr encryption
Nostr's current versioned encryption scheme for direct messages and other private payloads, using ChaCha20 with HMAC-SHA256 and padded ciphertext.
NIP-44 is Nostr's current encryption scheme for direct messages and other private payloads. It uses ChaCha20 for encryption with HMAC-SHA256 for authentication and derives the shared key via Elliptic-Curve Diffie-Hellman on the secp256k1 curve. The payload is padded so the ciphertext length does not leak the plaintext length.
NIP-44 replaces the original NIP-04, which had several well-known weaknesses. NIP-04 used AES-CBC without proper authentication, leaked message length, and let an attacker tamper with the ciphertext without being detected. NIP-44 fixes those problems while keeping the same underlying key material: the user's existing Nostr keypair.
NIP-44 is rarely used on its own. In practice, clients wrap NIP-44 ciphertext in the Private DMs gift-wrap construction (NIP-17 and NIP-59) so that relays cannot see who is talking to whom.