Node.js crypto.publicDecrypt()用法及代碼示例

crypto.publicDecrypt()方法用於使用先前已使用相應私鑰加密的 key (即crypto.privateEncrypt()方法)解密緩衝區的內容。

用法:

crypto.publicDecrypt( key, buffer )

參數：此方法接受兩個參數，如avobe所述，如下所述：

key:它的類型為Object，string，Buffer或KeyObject，並包含以下兩個參數：
1. passphrase:對於私鑰，它是可選的，其類型為字符串或緩衝區。
2. padding:它是在crypto.constants中定義的可選填充值，可以是crypto.constants.RSA_NO_PADDING或crypto.constants.RSA_PKCS1_PADDING。它是crypto.constants類型。
buffer它的類型為Buffer，TypedArray或DataView。

返回類型：它返回帶有解密內容的新緩衝區。

以下示例說明了Node.js中crypto.publicDecrypt()方法的使用：

範例1：

// Node.js program to demonstrate the  
// crypto.publicDecrypt() method 
  
// Including crypto, path, and fs module 
var crypto = require('crypto'); 
var fs = require('fs'); 
const path = require('path'); 
  
// Generating key files 
function generateKeyFiles() { 
  
    const keyPair = crypto.generateKeyPairSync('rsa', { 
        modulusLength:520, 
        publicKeyEncoding:{ 
            type:'spki', 
            format:'pem'
        }, 
        privateKeyEncoding:{ 
        type:'pkcs8', 
        format:'pem', 
        cipher:'aes-256-cbc', 
        passphrase:''
        } 
    }); 
       
    // Creating public and private key file  
    fs.writeFileSync("public_key", keyPair.publicKey); 
    fs.writeFileSync("private_key", keyPair.privateKey); 
} 
  
// Generate keys 
generateKeyFiles(); 
  
// Reading private key file 
var PRIVKEY = fs.readFileSync(path.join(__dirname, 
                          'private_key'), 'utf8'); 
  
// Reading public key file 
var PUBKEY = fs.readFileSync(path.join(__dirname, 
                          'public_key'), 'utf8'); 
  
// Defining my msg 
myMSG = "GeeksforGeeks!"; 
console.log("Original msg is:"+myMSG); 
  
// RSA PRIVATE ENCRYPT -> PUBLIC DECRYPT 
function privENC_pubDEC(originMSG){ 
  
  // Encrypting msg with privateEncrypt method 
 encmsg = crypto.privateEncrypt(PRIVKEY, 
               Buffer.from(originMSG, 'utf8') ) 
.toString('base64'); 
  
 // Decrypting msg with publicDecrypt method 
 msg = crypto.publicDecrypt(PUBKEY, 
              Buffer.from(encmsg, 'base64')); 
  
 console.log(); 
  
 // Prints encrypted msg 
 console.log("Encrypted with private key:"
                      + encmsg); 
  
 console.log(); 
  
 // Prints decrypted msg 
 console.log("Decrypted with public key:"
                     + msg.toString()); 
} 
  
// Calling privENC_pubDEC() method 
privENC_pubDEC(myMSG);

輸出：

Original msg is:GeeksforGeeks!

Encrypted with private key:
knwqke0ZrpJj1sLtL978OyqBMnJUEAEgTy1qJbyEnJyWbjoQ6hO7f
2FPnVhJnZwpZlxLbFQZCV1GMmr6WWJenFo=

Decrypted with public key:GeeksforGeeks!

範例2：

// Node.js program to demonstrate the  
// crypto.publicDecrypt() method 
  
// Including the fs and crypto modules 
var crypto = require('crypto'); 
var fs = require('fs'); 
  
// Reading the Private Key 
privK = fs.readFileSync('priv.key').toString(); 
  
// Passing the text to be encrypted 
// using private key 
var buf = Buffer.from('rishabh', 'utf8'); 
  
// Encrypting the text 
secretData = crypto.privateEncrypt(privK, buf); 
  
// Printing the encrypted text 
console.log(secretData); 
  
// Reading the Public key 
pubK = fs.readFileSync('pub.key').toString(); 
  
// Decrypting the text using public key 
origData = crypto.publicDecrypt(pubK, secretData); 
  
// Printing the original content 
console.log(origData);

輸出：

// Buffer 27 62 a1 2a 53 8d 0d 52 c7 3f e8 cc 89 42 c6
3e 8e 60 cd d3 57 06 d4 c9 1e 31 ba e6 23 8b 2c 10 be 
c1 fc ed 53 a4 9f f9 e0 5b da 74 d7 c2ca d0 98 f4 ... 
// Buffer 72 69 73 68 61 62 68

參考： https://nodejs.org/api/crypto.html#crypto_crypto_publicdecrypt_key_buffer

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