vector-core 0.3.0

//! Raw-key NIP-44 v2 sealing — the single symmetric-encryption primitive of the
//! Community protocol. The channel key (message plane) and the server-root key
//! (metadata plane) are both raw 32-byte `ConversationKey`s; ciphertext is
//! base64'd for carriage in an event's string `content` field.

use nostr_sdk::nips::nip44::v2::{decrypt_to_bytes, encrypt_to_bytes, ConversationKey};

/// Encrypt `plaintext` under a raw 32-byte key, returning base64 for event content.
pub fn seal(key: &[u8; 32], plaintext: &[u8]) -> Result<String, String> {
    let ck = ConversationKey::new(*key);
    let ciphertext = encrypt_to_bytes(&ck, plaintext).map_err(|e| e.to_string())?;
    Ok(base64_simd::STANDARD.encode_to_string(&ciphertext))
}

/// Inverse of [`seal`]: base64-decode then NIP-44-decrypt under the raw key. A
/// wrong key or tampered payload fails the MAC and returns `Err`.
pub fn open(key: &[u8; 32], content_b64: &str) -> Result<Vec<u8>, String> {
    let ciphertext = base64_simd::STANDARD
        .decode_to_vec(content_b64.as_bytes())
        .map_err(|e| e.to_string())?;
    let ck = ConversationKey::new(*key);
    decrypt_to_bytes(&ck, &ciphertext).map_err(|e| e.to_string())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn round_trip() {
        let key = [0x5au8; 32];
        let sealed = seal(&key, b"hello community").unwrap();
        assert_eq!(open(&key, &sealed).unwrap(), b"hello community");
    }

    #[test]
    fn wrong_key_fails() {
        let sealed = seal(&[1u8; 32], b"secret").unwrap();
        assert!(open(&[2u8; 32], &sealed).is_err());
    }

    #[test]
    fn distinct_ciphertext_per_call() {
        let key = [9u8; 32];
        assert_ne!(seal(&key, b"x").unwrap(), seal(&key, b"x").unwrap());
    }
}