Rolling Code vs Fixed Code: 3 Wireless Encoding Types Compared固定码 vs 学习码 vs 滚动码：3 种无线编码安全性实测

Your garage remote can be copied with a $0.50 cloner. Because 90%+ of low-end remotes use fixed code — press the button, it sends the same code every time.你的车库遥控器，别人花 30 块买个"拷贝器"就能复制。因为市面上 90% 以上的低端遥控器用的是固定码——按一下发一串永远不变的码。

At Huangshan Meirun, we help clients upgrade from fixed code to rolling code every year. Here's the full comparison.作为黄山美润电子的工程师，我们每年帮客户从固定码升级到滚动码。今天把 3 种编码方式全摊开讲。

1. How Each Encoding Works一、3 种编码方式原理

Fixed Code (PT2262)固定码（PT2262）

• Same code every press. "10110010" × 100 times = still "10110010"每次按键发射的编码完全一样。"10110010" 按 100 次还是 "10110010"
• Code space: 256 ~ 4,096 combinations (8~12 tri-state bits)地址码空间：256 ~ 4096 种（8~12 位三态编码）

Learning Code (EV1527)学习码（EV1527）

• Fixed code per remote, but receiver can "learn" multiple remotes遥控器发固定码，但接收端可以"学习"多个遥控器
• 20-bit address → 1M+ combinations. Still vulnerable to record-and-replay20 位地址码，100 万+ 组合。但码本身不变，仍可被录码复制

Rolling Code (HCS301 / KEELOQ)滚动码（HCS301 / KEELOQ）

• Code changes automatically every press. Record current code → next code is already different每次按键编码自动变化。录下当前码 → 下次发射的码已经变了
• 2³² = 4.2 billion combinations. Theoretically un-brute-forceable2³² = 42 亿种组合，理论不可穷举

2. Security Comparison二、安全性对比

3. KEELOQ Algorithm (Simplified)三、KEELOQ 滚动码算法原理

1. Factory: burn unique 64-bit key into each remote
   Key = f(Manufacturer Key, Serial Number)

2. Each button press:
   - Sync counter +1 (16-bit, 0~65535 cyclic)
   - Encrypted = KEELOQ_ENCRYPT(Key, Counter || Fixed)
   - Transmit: [Serial] + [Encrypted] + [Button]

3. Receiver:
   - Decrypt with same key
   - Verify counter in window (current ±16)
   - Valid → execute, update counter
   - Invalid → reject1. 出厂：烧录 64 位加密密钥
   Key = f(厂方密钥, 序列号)

2. 每次按键：
   - 同步计数器 +1（16 位，0~65535 循环）
   - 加密码 = KEELOQ_ENCRYPT(密钥, 计数器 || 固定码)
   - 发射：[序列号] + [加密码] + [按键值]

3. 接收端：
   - 同一密钥解密
   - 验证计数器在窗口内（当前值 ±16）
   - 通过 → 执行，更新计数器
   - 不通过 → 拒绝

4. Chip Comparison四、3 种芯片实战对比

5. When to Use Each五、什么场景该用什么码

6. Factory Pitfalls六、工厂实战避坑

1. HCS301 needs key programmingHCS301 需要烧录密钥 — can't buy blanks and solder. Factory: buy blanks → programmer → SMT不能直接买空片贴板。流程：采购空片 → 编程器烧录 → 贴片
2. Sync counter overflow同步计数器溢出 — 16-bit wraps at 65535, receiver firmware must handle16 位循环，65535 回到 0，接收端固件要处理回绕
3. Limited learn capacity学习数量限制 — HCS301: 4~8 remotes max. Need 30 remotes? Use EV1527 insteadHCS301 限制 4~8 个遥控器。需要 30 个？用 EV1527 更实际
4. Debugging difficulty调试难度 — Fixed code: logic analyzer. Rolling code: KEELOQ decrypt tools固定码用逻辑分析仪，滚动码需要 KEELOQ 解密工具
5. Chip supply risk芯片缺货 — HCS301 = Microchip proprietary. We also support Chinese-compatible alternativesHCS301 是 Microchip 专有。我们也支持国产兼容方案

7. Real Cases七、真实案例

• Garage door brand某品牌车库门: HCS301 + 433MHz, 100k/yr. Zero security complaints (was 20+/month with fixed code)：HCS301 + 433MHz，年产 10 万套。0 起安全投诉（之前用固定码每月 20+ 起）
• Parking system某停车场: EV1527 + 315MHz, 30 remotes/receiver, cost-optimal：EV1527 + 315MHz，30 遥控配 1 接收，成本最优
• Smart home OEM某智能家居品牌: HCS301 + AES-128 dual encryption, EU/US export：HCS301 + AES-128 双重加密，出口欧美