Decipher 类

• 继承自: <stream.Transform>

Decipher 类的实例用于解密数据。 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，其中写入纯加密数据以在可读端生成未加密数据，或
• 使用 decipher.update() 和 decipher.final() 方法生成未加密的数据。

crypto.createDecipher() 或 crypto.createDecipheriv() 方法用于创建 Decipher 实例。 Decipher 对象不能直接使用 new 关键字创建。

示例：使用 Decipher 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);
// IV 通常与密文一起传入。
const iv = Buffer.alloc(16, 0); // 初始化向量。

const decipher = crypto.createDecipheriv(algorithm, key, iv);

let decrypted = '';
decipher.on('readable', () => {
  while (null !== (chunk = decipher.read())) {
    decrypted += chunk.toString('utf8');
  }
});
decipher.on('end', () => {
  console.log(decrypted);
  // 打印: some clear text data
});

// 使用相同的算法、密钥和 iv 加密。
const encrypted =
  'e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa';
decipher.write(encrypted, 'hex');
decipher.end();

示例：使用 Decipher 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);
// IV 通常与密文一起传入。
const iv = Buffer.alloc(16, 0); // 初始化向量。

const decipher = crypto.createDecipheriv(algorithm, key, iv);

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

input.pipe(decipher).pipe(output);

示例：使用 decipher.update() 和 decipher.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);
// IV 通常与密文一起传入。
const iv = Buffer.alloc(16, 0); // 初始化向量。

const decipher = crypto.createDecipheriv(algorithm, key, iv);

// 使用相同的算法、密钥和 iv 加密。
const encrypted =
  'e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa';
let decrypted = decipher.update(encrypted, 'hex', 'utf8');
decrypted += decipher.final('utf8');
console.log(decrypted);
// 打印: some clear text data

• Extends: <stream.Transform>

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

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

The crypto.createDecipher() or crypto.createDecipheriv() methods are used to create Decipher instances. Decipher objects are not to be created directly using the new keyword.

Example: Using Decipher 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 the async `crypto.scrypt()` instead.
const key = crypto.scryptSync(password, 'salt', 24);
// The IV is usually passed along with the ciphertext.
const iv = Buffer.alloc(16, 0); // Initialization vector.

const decipher = crypto.createDecipheriv(algorithm, key, iv);

let decrypted = '';
decipher.on('readable', () => {
  while (null !== (chunk = decipher.read())) {
    decrypted += chunk.toString('utf8');
  }
});
decipher.on('end', () => {
  console.log(decrypted);
  // Prints: some clear text data
});

// Encrypted with same algorithm, key and iv.
const encrypted =
  'e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa';
decipher.write(encrypted, 'hex');
decipher.end();

Example: Using Decipher 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);
// The IV is usually passed along with the ciphertext.
const iv = Buffer.alloc(16, 0); // Initialization vector.

const decipher = crypto.createDecipheriv(algorithm, key, iv);

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

input.pipe(decipher).pipe(output);

Example: Using the decipher.update() and decipher.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);
// The IV is usually passed along with the ciphertext.
const iv = Buffer.alloc(16, 0); // Initialization vector.

const decipher = crypto.createDecipheriv(algorithm, key, iv);

// Encrypted using same algorithm, key and iv.
const encrypted =
  'e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa';
let decrypted = decipher.update(encrypted, 'hex', 'utf8');
decrypted += decipher.final('utf8');
console.log(decrypted);
// Prints: some clear text data