Cipher 类

• 继承自: <stream.Transform>

Cipher 类的实例用于加密数据。 可以通过以下两种方式之一使用该类：

• 作为既可读又可写的流，其中写入未加密的纯数据以在可读端生成加密的数据，或
• 使用 cipher.update() 和 cipher.final() 方法生成加密的数据。

crypto.createCipher() 或 crypto.createCipheriv() 方法用于创建 Cipher 实例。 Cipher 对象不能直接使用 new 关键字创建。

示例：使用 Cipher 对象作为流：

const crypto = require('crypto');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';
// 密钥长度取决于算法。
// 在这种情况下，对于 aes192，它是 24 字节（192 位）。
// 请改用异步的 `crypto.scrypt()`。
const key = crypto.scryptSync(password, 'salt', 24);
// 使用 `crypto.randomBytes()` 生成随机的 iv，
// 而不是此处显示的静态的 iv。
const iv = Buffer.alloc(16, 0); // 初始化向量。

const cipher = crypto.createCipheriv(algorithm, key, iv);

let encrypted = '';
cipher.on('readable', () => {
  let chunk;
  while (null !== (chunk = cipher.read())) {
    encrypted += chunk.toString('hex');
  }
});
cipher.on('end', () => {
  console.log(encrypted);
  // 打印: e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa
});

cipher.write('some clear text data');
cipher.end();

示例：使用 Cipher 和管道流：

const crypto = require('crypto');
const fs = require('fs');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';
// 请改用异步的 `crypto.scrypt()`。
const key = crypto.scryptSync(password, 'salt', 24);
// 使用 `crypto.randomBytes()` 生成随机的 iv，
// 而不是此处显示的静态的 iv。
const iv = Buffer.alloc(16, 0); // 初始化向量。

const cipher = crypto.createCipheriv(algorithm, key, iv);

const input = fs.createReadStream('test.js');
const output = fs.createWriteStream('test.enc');

input.pipe(cipher).pipe(output);

示例：使用 cipher.update() 和 cipher.final() 方法：

const crypto = require('crypto');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';
// 请改用异步的 `crypto.scrypt()`。
const key = crypto.scryptSync(password, 'salt', 24);
// 使用 `crypto.randomBytes` 生成随机的 iv，
// 而不是此处显示的静态的 iv。
const iv = Buffer.alloc(16, 0); // 初始化向量。

const cipher = crypto.createCipheriv(algorithm, key, iv);

let encrypted = cipher.update('some clear text data', 'utf8', 'hex');
encrypted += cipher.final('hex');
console.log(encrypted);
// 打印: e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa

• Extends: <stream.Transform>

Instances of the Cipher class are used to encrypt data. The class can be used in one of two ways:

• As a stream that is both readable and writable, where plain unencrypted data is written to produce encrypted data on the readable side, or
• Using the cipher.update() and cipher.final() methods to produce the encrypted data.

The crypto.createCipher() or crypto.createCipheriv() methods are used to create Cipher instances. Cipher objects are not to be created directly using the new keyword.

Example: Using Cipher objects as streams:

const crypto = require('crypto');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';
// Key length is dependent on the algorithm. In this case for aes192, it is
// 24 bytes (192 bits).
// Use async `crypto.scrypt()` instead.
const key = crypto.scryptSync(password, 'salt', 24);
// Use `crypto.randomBytes()` to generate a random iv instead of the static iv
// shown here.
const iv = Buffer.alloc(16, 0); // Initialization vector.

const cipher = crypto.createCipheriv(algorithm, key, iv);

let encrypted = '';
cipher.on('readable', () => {
  let chunk;
  while (null !== (chunk = cipher.read())) {
    encrypted += chunk.toString('hex');
  }
});
cipher.on('end', () => {
  console.log(encrypted);
  // Prints: e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa
});

cipher.write('some clear text data');
cipher.end();

Example: Using Cipher and piped streams:

const crypto = require('crypto');
const fs = require('fs');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';
// Use the async `crypto.scrypt()` instead.
const key = crypto.scryptSync(password, 'salt', 24);
// Use `crypto.randomBytes()` to generate a random iv instead of the static iv
// shown here.
const iv = Buffer.alloc(16, 0); // Initialization vector.

const cipher = crypto.createCipheriv(algorithm, key, iv);

const input = fs.createReadStream('test.js');
const output = fs.createWriteStream('test.enc');

input.pipe(cipher).pipe(output);

Example: Using the cipher.update() and cipher.final() methods:

const crypto = require('crypto');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';
// Use the async `crypto.scrypt()` instead.
const key = crypto.scryptSync(password, 'salt', 24);
// Use `crypto.randomBytes` to generate a random iv instead of the static iv
// shown here.
const iv = Buffer.alloc(16, 0); // Initialization vector.

const cipher = crypto.createCipheriv(algorithm, key, iv);

let encrypted = cipher.update('some clear text data', 'utf8', 'hex');
encrypted += cipher.final('hex');
console.log(encrypted);
// Prints: e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa