stellar.ts

import nacl from "tweetnacl";

/**
 * Stellar StrKey encoding for ed25519 public keys.
 * Ported from open-signer's shared/cryptography/src/primitives/encoding/strkey.ts
 * to remove the @stellar/stellar-sdk dependency.
 */

const ED25519_PUBLIC_KEY_VERSION_BYTE = 6 << 3; // "G" prefix when base32-encoded

const BASE32_ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";

// CRC16-XModem lookup table (from Stellar's implementation)
// prettier-ignore
const CRC16_TABLE = [
    0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7, 0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad,
    0xe1ce, 0xf1ef, 0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6, 0x9339, 0x8318, 0xb37b, 0xa35a,
    0xd3bd, 0xc39c, 0xf3ff, 0xe3de, 0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485, 0xa56a, 0xb54b,
    0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d, 0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
    0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc, 0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861,
    0x2802, 0x3823, 0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b, 0x5af5, 0x4ad4, 0x7ab7, 0x6a96,
    0x1a71, 0x0a50, 0x3a33, 0x2a12, 0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a, 0x6ca6, 0x7c87,
    0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41, 0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
    0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70, 0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a,
    0x9f59, 0x8f78, 0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f, 0x1080, 0x00a1, 0x30c2, 0x20e3,
    0x5004, 0x4025, 0x7046, 0x6067, 0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e, 0x02b1, 0x1290,
    0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256, 0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
    0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405, 0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e,
    0xc71d, 0xd73c, 0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634, 0xd94c, 0xc96d, 0xf90e, 0xe92f,
    0x99c8, 0x89e9, 0xb98a, 0xa9ab, 0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3, 0xcb7d, 0xdb5c,
    0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a, 0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92,
    0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9, 0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83,
    0x1ce0, 0x0cc1, 0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8, 0x6e17, 0x7e36, 0x4e55, 0x5e74,
    0x2e93, 0x3eb2, 0x0ed1, 0x1ef0,
];

function crc16Xmodem(data: Uint8Array): Uint8Array {
    let crc = 0x0;
    for (let i = 0; i < data.length; i++) {
        const byte = data[i]!;
        crc = ((crc << 8) ^ CRC16_TABLE[((crc >> 8) ^ byte)!]!) & 0xffff;
    }
    const checksum = new Uint8Array(2);
    checksum[0] = crc & 0xff;
    checksum[1] = (crc >> 8) & 0xff;
    return checksum;
}

function base32Encode(data: Uint8Array): string {
    let bits = 0;
    let value = 0;
    let output = "";

    for (let i = 0; i < data.length; i++) {
        value = (value << 8) | data[i]!;
        bits += 8;
        while (bits >= 5) {
            output += BASE32_ALPHABET[(value >>> (bits - 5)) & 31];
            bits -= 5;
        }
    }
    if (bits > 0) {
        output += BASE32_ALPHABET[(value << (5 - bits)) & 31];
    }
    while (output.length % 8 !== 0) {
        output += "=";
    }
    return output;
}

/**
 * Encode a 32-byte ed25519 public key as a Stellar StrKey address (G... format).
 */
export function encodeStellarPublicKey(publicKeyBytes: Uint8Array): string {
    const payload = new Uint8Array(1 + publicKeyBytes.length);
    payload[0] = ED25519_PUBLIC_KEY_VERSION_BYTE;
    payload.set(publicKeyBytes, 1);

    const checksum = crc16Xmodem(payload);
    const unencoded = new Uint8Array(payload.length + 2);
    unencoded.set(payload, 0);
    unencoded.set(checksum, payload.length);

    return base32Encode(unencoded);
}

/**
 * Derive an ed25519 keypair from a 32-byte seed and return the public key bytes
 * and a signing function compatible with the Stellar server signer.
 */
export function ed25519KeypairFromSeed(seed: Uint8Array): {
    publicKey: Uint8Array;
    secretKey: Uint8Array;
} {
    const keypair = nacl.sign.keyPair.fromSeed(seed);
    return { publicKey: keypair.publicKey, secretKey: keypair.secretKey };
}

/**
 * Sign a message using ed25519 (detached signature).
 */
export function ed25519Sign(message: Uint8Array, secretKey: Uint8Array): Uint8Array {
    return nacl.sign.detached(message, secretKey);
}