RSAUtils

import java.io.ByteArrayOutputStream;
import java.util.Base64;
import javax.crypto.Cipher;
import java.security.Key;
import java.security.KeyFactory;
import java.security.spec.X509EncodedKeySpec;

/**
* RSA public key encryption/decryption utility class
* <p>
* Provides asymmetric encryption and decryption based on public key,
* suitable for encrypted data transmission in API communication.
*/
public class RSAUtils {
  // RSA encryption maximum block size (unit: bytes)
  private static final int MAX_ENCRYPT_BLOCK = 117;

  /**
   * Encrypt data using public key
   *
   * @param data Original binary data
   * @param publicKey Base64 encoded public key string
   * @return Encrypted binary data
   *
   * Usage scenario: Encrypt business data before sending API requests.
   * Automatically handles chunked encryption of large data (117 bytes/chunk).
   *
   * Example:
   * byte[] encrypted = RSAUtils.encryptByPublicKey(
   *     jsonData.getBytes(),
   *     "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQ..."
   * );
   */
  public static byte[] encryptByPublicKey(byte[] data, String publicKey) throws Exception {
      // 1. Base64 decode public key
      byte[] keyBytes = Base64Util.decodeString(publicKey);

      // 2. Generate public key object
      KeyFactory keyFactory = KeyFactory.getInstance("RSA");
      Key publicK = keyFactory.generatePublic(
          new X509EncodedKeySpec(keyBytes)
      );

      // 3. Create and initialize cipher
      Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
      cipher.init(Cipher.ENCRYPT_MODE, publicK);

      // 4. Chunked encryption for large data
      int inputLen = data.length;
      int offset = 0;
      java.io.ByteArrayOutputStream out = new java.io.ByteArrayOutputStream();

      while (inputLen - offset > 0) {
          int blockSize = Math.min(inputLen - offset, MAX_ENCRYPT_BLOCK);
          byte[] encryptedBlock = cipher.doFinal(data, offset, blockSize);
          out.write(encryptedBlock, 0, encryptedBlock.length);
          offset += blockSize;
      }

      return out.toByteArray();
  }

  /**
   * Decrypt data using public key
   *
   * @param encryptedData Encrypted binary data
   * @param publicKey Base64 encoded public key string
   * @return Decrypted original binary data
   *
   * Usage scenario: Decrypt encrypted data returned from APIs.
   * Suitable for one-time decryption of small data chunks.
   *
   * Example:
   * byte[] decrypted = RSAUtils.decryptByPublicKey(
   *     encryptedBytes,
   *     "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQ..."
   * );
   */
  public static byte[] decryptByPublicKey(byte[] encryptedData, String publicKey) throws Exception {

      final int MAX_DECRYPT_BLOCK = 128;

      // 1. Base64 decode public key
      byte[] keyBytes = Base64Util.decodeString(publicKey);

      // 2. Generate public key object
      KeyFactory keyFactory = KeyFactory.getInstance("RSA");
      Key publicK = keyFactory.generatePublic(
          new X509EncodedKeySpec(keyBytes)
      );

      // 3. Create and initialize decrypter
      Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
      cipher.init(Cipher.DECRYPT_MODE, publicK);

      // 4. One-time decryption (suitable for small data)
      // return cipher.doFinal(encryptedData);
      int inputLen = encryptedData.length;
      ByteArrayOutputStream out = new ByteArrayOutputStream();
      int offSet = 0;
      byte[] cache;
      int i = 0;
      // Decrypt data in segments
      while (inputLen - offSet > 0) {
          if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
              cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
          } else {
              cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
          }
          out.write(cache, 0, cache.length);
          i++;
          offSet = i * MAX_DECRYPT_BLOCK;
      }
      byte[] decryptedData = out.toByteArray();
      out.close();
      return decryptedData;
  }
}

const crypto = require('crypto');
const Base64Util = require('./Base64Util');

/**
* RSA Public Key Encryption/Decryption Utility Class
*
* Provides asymmetric encryption and decryption capabilities based on public keys,
* suitable for secure data transmission in API communications.
*/
class RSAUtils {
  // Maximum block size for RSA encryption (in bytes)
  static MAX_ENCRYPT_BLOCK = 117;

  /**
   * Encrypts data using a public key
   * @param {Buffer} data - Raw binary data to be encrypted
   * @param {string} publicKey - Base64 encoded public key string
   * @returns {Buffer} Encrypted binary data
   *
   * Usage scenario: Encrypts business data before sending API requests.
   * Automatically handles large data segmentation (117 bytes per block).
   */
  static encryptByPublicKey(data, publicKey) {
      try {
          // 1. Convert Base64 public key to PEM format
          const pemKey = `-----BEGIN PUBLIC KEY-----\n${publicKey}\n-----END PUBLIC KEY-----`;

          // 2. Generate public key object
          const key = crypto.createPublicKey(pemKey);

          // 3. Create and initialize encryptor
          const encryptedParts = [];
          const buffer = Buffer.from(data);
          let offset = 0;
          const inputLen = buffer.length;

          // 4. Segment and encrypt large data
          while (offset < inputLen) {
              const blockSize = Math.min(inputLen - offset, RSAUtils.MAX_ENCRYPT_BLOCK);
              const chunk = buffer.slice(offset, offset + blockSize);
              const encryptedChunk = crypto.publicEncrypt({
                  key: key,
                  padding: crypto.constants.RSA_PKCS1_PADDING
              }, chunk);
              encryptedParts.push(encryptedChunk);
              offset += blockSize;
          }

          return Buffer.concat(encryptedParts);
      } catch (error) {
          throw new Error(`RSA encryption failed: ${error.message}`);
      }
  }

  /**
   * Decrypts data using a public key
   * @param {Buffer} encryptedData - Encrypted binary data
   * @param {string} publicKey - Base64 encoded public key string
   * @returns {Buffer} Decrypted raw binary data
   *
   * Usage scenario: Decrypts encrypted data returned from API responses.
   * Automatically handles large data segmentation (128 bytes per block).
   */
  static decryptByPublicKey(encryptedData, publicKey) {
      try {
          // 1. Convert Base64 public key to PEM format
          const pemKey = `-----BEGIN PUBLIC KEY-----\n${publicKey}\n-----END PUBLIC KEY-----`;

          // 2. Generate public key object
          const key = crypto.createPublicKey(pemKey);

          // 3. Create and initialize decryptor
          const decryptedParts = [];
          const buffer = Buffer.from(encryptedData);
          let offset = 0;
          const inputLen = buffer.length;
          const MAX_DECRYPT_BLOCK = 128;

          // 4. Segment and decrypt data
          while (offset < inputLen) {
              const blockSize = Math.min(inputLen - offset, MAX_DECRYPT_BLOCK);
              const chunk = buffer.slice(offset, offset + blockSize);
              const decryptedChunk = crypto.publicDecrypt({
                  key: key,
                  padding: crypto.constants.RSA_PKCS1_PADDING
              }, chunk);
              decryptedParts.push(decryptedChunk);
              offset += blockSize;
          }

          return Buffer.concat(decryptedParts);
      } catch (error) {
          throw new Error(`RSA decryption failed: ${error.message}`);
      }
  }
}

module.exports = RSAUtils;

import base64
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import padding
from cryptography.hazmat.backends import default_backend

class RSAUtils:
# RSA encryption maximum block size (unit: bytes)
MAX_ENCRYPT_BLOCK = 117

@staticmethod
def encrypt_by_public_key(data: bytes, public_key_str: str) -> bytes:
    """
    Encrypt data using public key
    @param data: Original binary data
    @param public_key_str: Base64 encoded public key string
    @return: Encrypted binary data

    Usage scenario: Encrypt business data before sending API requests
    Automatically handles chunked encryption of large data (117 bytes/chunk)
    """
    # 1. Base64 decode public key
    public_key_der = base64.b64decode(public_key_str)

    # 2. Load public key object
    public_key = serialization.load_der_public_key(
        public_key_der,
        backend=default_backend()
    )

    # 3. Chunked encryption
    offset = 0
    encrypted_chunks = []
    while offset < len(data):
        block = data[offset:offset + RSAUtils.MAX_ENCRYPT_BLOCK]
        encrypted_chunk = public_key.encrypt(
            block,
            padding.OAEP(
                mgf=padding.MGF1(algorithm=hashes.SHA256()),
                algorithm=hashes.SHA256(),
                label=None
            )
        )
        encrypted_chunks.append(encrypted_chunk);
        offset += len(block)

    return b''.join(encrypted_chunks)

@staticmethod
def decrypt_by_public_key(encrypted_data: bytes, public_key_str: str) -> bytes:
    """
    Decrypt data using public key
    @param encrypted_data: Encrypted binary data
    @param public_key_str: Base64 encoded public key string
    @return: Decrypted original binary data

    Usage scenario: Decrypt encrypted data returned from APIs
    Suitable for one-time decryption of small data chunks
    """
    # 1. Base64 decode public key
    public_key_der = base64.b64decode(public_key_str)

    # 2. Load public key object
    public_key = serialization.load_der_public_key(
        public_key_der,
        backend=default_backend()
    )

    # 3. One-time decryption
    return public_key.decrypt(
        encrypted_data,
        padding.OAEP(
            mgf=padding.MGF1(algorithm=hashes.SHA256()),
            algorithm=hashes.SHA256(),
            label=None
        )
    )

# Usage example
if __name__ == "__main__":
# Simulate public key string
public_key = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQ..."

# Data to encrypt
data = b"Sensitive data 12345"

try:
    # Encryption
    encrypted = RSAUtils.encrypt_by_public_key(data, public_key)
    print("Encryption result:", base64.b64encode(encrypted).decode())

    # Decryption
    decrypted = RSAUtils.decrypt_by_public_key(encrypted, public_key)
    print("Decryption result:", decrypted.decode())
except Exception as e:
    print("RSA operation failed:", e)