Decryption of messages containing the sensitive information

const crypto = require('crypto');

const message = '... content of message ...';
const sign = '... value of x-sign header ...';
const privateKey = '... private key ...';

const decryptDataWithPrivateKey = (encryptedData, privateKey) => {
    const ciphertext = Buffer.from(encryptedData, 'base64');
    const decryptedData = crypto.privateDecrypt(
        {
          key: privateKey,
          padding: crypto.constants.RSA_PKCS1_OAEP_PADDING,
        },
        ciphertext
    );

    return decryptedData.toString();
}

const decryptContent = (messageBase64, keyBase64) => {
    const ivSize = 16;
    const aesKey = Buffer.from(keyBase64, 'utf8');
    const iv = Buffer.from(messageBase64.slice(0, ivSize), 'utf8')
    const encryptedTextBase64 = messageBase64.slice(ivSize, messageBase64.length);
    const decipher = crypto.createDecipheriv('aes-256-cbc', aesKey, iv);
    const decrypted = decipher.update(encryptedTextBase64, 'base64', 'utf8');
    return decrypted + decipher.final('utf8');
}

const decryptedSecret = decryptDataWithPrivateKey(sign, privateKey);
const content = decryptContent(message, decryptedSecret);
console.log('Decrypted content:');
console.log(content);