安全研究人员对广泛使用的Flume Water Monitor智能水表设备进行了安全分析，发现其915 MHz通信协议存在关键弱点 [1]。该设备通过在902.5-927 MHz频段的50个信道中进行跳频与桥接设备通信，采用2-FSK调制和200 kbps数据速率 [1]。负载采用AES-128 ECB模式加密，但密钥生成机制存在设计缺陷 [1]。
研究人员发现，128位密钥由8字节硬编码密钥衍生，结合未加密报头字节后，有效密钥空间仅为44位，而非理论上的128位 [1]。利用这一弱点，研究团队通过非优化的Python脚本在GPU上花费约一天时间即成功暴力破解密钥，云平台成本不足10美元 [1]。破解后的密钥可被用于生成欺骗性消息，可能启用恶意固件更新 [1]。
Flume公司已知悉此分析结果，并表示已有进一步改进隐私和安全的计划，同意公开发布此研究分析 [1]。
Security researchers have successfully broken the encryption protecting Flume Water Monitor, a widely deployed smart water meter that communicates with bridge devices over the 915 MHz frequency band [1]. The attack exploited weaknesses in the device's cryptographic implementation, reducing the effective key space from 128 bits to just 44 bits through a combination of factors including hardcoded key derivation and unencrypted header bytes [1].
The researchers detailed how the device implements frequency hopping across 50 channels between 902.5 and 927 MHz with 500 kHz spacing and uses 2-FSK modulation at 200 kbps to transmit data [1]. Payloads of 16 bytes are encrypted using AES-128 ECB mode, but the 128-bit key is derived from an 8-byte key through simple hardcoded mapping, substantially weakening the security [1]. Using a non-optimized Python script running on GPU hardware, the team required approximately one day of computation to brute-force the encryption, with cloud platform costs falling below $10 [1]. The vulnerability is particularly concerning because anyone possessing the AES key and knowledge of the CRC algorithm could generate fraudulent messages capable of triggering malicious firmware updates [1].
Flume acknowledged the findings and indicated plans for further improvements to privacy and security protections [1]. The company agreed to allow public release of the security analysis [1].