Class PowCaptchaGenerator

java.lang.Object
cloud.opencode.base.captcha.generator.AbstractCaptchaGenerator
cloud.opencode.base.captcha.generator.PowCaptchaGenerator
All Implemented Interfaces:
CaptchaGenerator
public final class PowCaptchaGenerator extends AbstractCaptchaGenerator implements CaptchaGenerator
Proof-of-Work Captcha Generator — Generates computational challenge for invisible verification 工作量证明验证码生成器 — 生成计算挑战用于无感验证

This generator creates a cryptographic challenge that requires the client to find a nonce such that SHA-256(challenge + nonce) has a specified number of leading zero bits.

此生成器创建一个加密挑战，要求客户端找到一个 nonce， 使得 SHA-256(challenge + nonce) 具有指定数量的前导零位。

PoW verification is invisible to users — the client-side JavaScript performs the computation automatically. A difficulty of 20 requires approximately 2^20 (~1M) hash operations, taking ~100ms-500ms on modern hardware.

PoW 验证对用户不可见 — 客户端 JavaScript 自动执行计算。 难度为 20 大约需要 2^20（~100万）次哈希操作，在现代硬件上大约需要 100ms-500ms。

Features | 主要功能:

  • Invisible verification (no user interaction required) - 无感验证（无需用户交互）
  • Configurable difficulty via leading zero bits - 通过前导零位配置难度
  • Cryptographically secure challenge generation - 加密安全的挑战生成
  • No image data (zero-byte imageData) - 无图像数据（零字节 imageData）
  • SHA-256 based proof-of-work - 基于 SHA-256 的工作量证明

Usage Examples | 使用示例:

CaptchaGenerator generator = new PowCaptchaGenerator();
CaptchaConfig config = CaptchaConfig.builder()
    .powDifficulty(20)
    .expireTime(Duration.ofMinutes(5))
    .build();
Captcha captcha = generator.generate(config);

// Client receives challenge and difficulty from metadata
String challenge = (String) captcha.getMetadata("challenge");
int difficulty = (int) captcha.getMetadata("difficulty");
// Client finds nonce such that SHA-256(challenge + nonce) has 'difficulty' leading zeros

Security | 安全性:

Performance | 性能:

  • Server-side generation is O(1) - 服务端生成为 O(1)
  • Client-side solving is O(2^difficulty) on average - 客户端求解平均为 O(2^difficulty)
  • Server-side validation is O(1) (single hash computation) - 服务端验证为 O(1)（单次哈希计算）
Since:
JDK 25, opencode-base-captcha V1.0.3
Author:
Leon Soo www.LeonSoo.com
See Also:

  • Constructor Details

    • PowCaptchaGenerator

      public PowCaptchaGenerator()

  • Method Details

    • getType

      public CaptchaType getType()
      Gets the supported CAPTCHA type. 获取支持的验证码类型。
      Specified by:
      getType in interface CaptchaGenerator
      Returns:
      the CAPTCHA type | 验证码类型

    • generate

      public Captcha generate(CaptchaConfig config)
      Generates a PoW CAPTCHA challenge. 生成 PoW 验证码挑战。

      The generated Captcha contains:

      生成的 Captcha 包含：

      • imageData: empty byte array (no image for PoW) - 空字节数组（PoW 无图像）
      • answer: "{challenge}:{difficulty}" format for validation - "{challenge}:{difficulty}" 格式用于验证
      • metadata: contains "challenge", "difficulty", and "algorithm" fields - 包含 "challenge"、"difficulty" 和 "algorithm" 字段
      Specified by:
      generate in interface CaptchaGenerator
      Parameters:
      config - the configuration (uses powDifficulty and expireTime) | 配置（使用 powDifficulty 和 expireTime）
      Returns:
      the generated PoW CAPTCHA | 生成的 PoW 验证码