如何实现Uint8Array与字符串互转及解决eccrypto解密报错

Hey, I see exactly what's going wrong here—let's break this down and fix it step by step.

问题根源 #

When you use JSON.stringify() on the encrypted object returned by eccrypto, all the Uint8Array fields (iv, ephemPublicKey, ciphertext, mac) get converted into plain JavaScript arrays (like [12, 34, 56]). But eccrypto.decrypt() expects Buffer or Uint8Array types for these fields, not regular arrays. That's why you're hitting the "bad public key" error—your parsed ephemPublicKey is no longer a valid cryptographic key type.

解决方案：序列化前转十六进制，解析后转回Buffer #

We need to convert each Uint8Array field to a hex string before serializing to JSON, then convert them back to Buffer (which is compatible with eccrypto) after parsing.

修改后的完整可运行代码 #

const eccrypto = require('eccrypto');

// B's public key (Buffer type)
const publicKeyB = Buffer.from("0418c7ced07c0c17f42b132747c70fddb6b31ea0ad349c2e9f800f48f0a73c2ea028d41b239077a48136ce546f9d2811bf1ec311c56e6a41f33906a1fc2472e451", 'hex');
// B's private key (Buffer type)
const privateKeyB = Buffer.from("9a2d66404b69023c2c45da81ca4b696a8234b7ae53ea6b7ffc0d6bdd0e0e3279", 'hex');

eccrypto.encrypt(publicKeyB, Buffer.from('Message to encrypt')).then(function(encrypted) {
  console.log('Original encrypted object:', encrypted);

  // Step 1: Convert Uint8Array fields to hex strings for JSON serialization
  const serializableEncrypted = {
    iv: encrypted.iv.toString('hex'),
    ephemPublicKey: encrypted.ephemPublicKey.toString('hex'),
    ciphertext: encrypted.ciphertext.toString('hex'),
    mac: encrypted.mac.toString('hex')
  };
  const encoded = JSON.stringify(serializableEncrypted);
  console.log('Serialized JSON:', encoded);

  // Step 2: Parse JSON and convert hex strings back to Buffer
  const parsed = JSON.parse(encoded);
  const actual = {
    iv: Buffer.from(parsed.iv, 'hex'),
    ephemPublicKey: Buffer.from(parsed.ephemPublicKey, 'hex'),
    ciphertext: Buffer.from(parsed.ciphertext, 'hex'),
    mac: Buffer.from(parsed.mac, 'hex')
  };
  console.log('Restored object after parsing:', actual);

  // Now decryption will work correctly
  eccrypto.decrypt(privateKeyB, actual).then(function(plaintext) {
    console.log("Decrypted message:", plaintext.toString());
  }).catch(err => {
    console.error('Decryption error:', err);
  });
}).catch(err => {
  console.error('Encryption error:', err);
});

Uint8Array与字符串的互转方法 #

For your question about converting Uint8Array to strings and back, hexadecimal strings are the best choice—they're compact, human-readable, and preserve all binary data perfectly:

1. Uint8Array → Hex String #

// Node.js (using Buffer, which is a subclass of Uint8Array)
const buf = Buffer.from([0x12, 0x34, 0x56]);
const hexStr = buf.toString('hex'); // Output: "123456"

// Browser-only pure Uint8Array conversion
function uint8ArrayToHex(arr) {
  return Array.from(arr)
    .map(byte => byte.toString(16).padStart(2, '0')) // Ensure 2-digit hex
    .join('');
}

2. Hex String → Uint8Array/Buffer #

// Node.js (convert to Buffer)
const buf = Buffer.from(hexStr, 'hex');

// Browser-only (convert to Uint8Array)
function hexToUint8Array(hexStr) {
  const arr = [];
  for (let i = 0; i < hexStr.length; i += 2) {
    arr.push(parseInt(hexStr.substr(i, 2), 16));
  }
  return new Uint8Array(arr);
}

Why Direct JSON.stringify Fails? #

JSON doesn't natively support binary types like Uint8Array or Buffer. It automatically converts these objects to their underlying array representations. When you parse the JSON back, you get a plain array instead of the original binary type—this breaks eccrypto's validation checks for cryptographic keys and data.

内容的提问来源于stack exchange，提问作者Shubham Dhakal