智能儀表適應新的歐洲標準

　　歐盟智能電網計劃闡明了智能電表的技術規范，這些標準現在正在成為法定任務。嚴格的時間、安全和電源要求提出了具有挑戰性的設計問題。新的MCU簡化遷移路徑。

　　歐洲聯盟國家最近制定了將歐盟智能電網倡議納入國家立法的法律。在德國，政府已決定改用智能計量2014，從而使能源供應商和電表制造商面臨壓力。能源經濟法（“energiewirtschaftsgesetz，”EnWG）要求米必須反映實際能耗和實際使用時間，“從2010年1月開始（§21b）。能源供應商有義務創造每月，每季度或半年的總數，“他們也有提供“負荷變化或白天依賴關稅”直到2010年12月（§40）。如果沒有某種數據傳輸工具，這些法律義務很難滿足。在這樣的背景下，VDE最近發布計量裝置兩種規格。規格系列EDL（edl21和edl40）涵蓋了德國4300萬家持有米近似，而對稱2（“同步模塊表”）在商業和工業領域的目標。

　　Both specifications employ elliptic curve cryptography （ECC） for creating digital signatures on consumption measurement values. In particular， the Elliptic Curve Digital Signature Algorithm （ECDSA） guarantees the authenticity of remote meter readings. Compared to other algorithms， like RSA， ECC provides the same level of security with shorter keys， or more security when the key-length is kept equal. For instance， an ECDSA signature with a key-length of 192 bits is slightly more secure than 1024-bit RSA. This is of particular importance in the context of embedded systems， since shorter keys require less memory and less computational power， resulting in a significant performance and energy-efficiency gain. This is why the ANSI-standardized curve p192r1 serves as the base curve for digitally signing measurements on SyM2 and EDL meters. However， SyM2 meters face stringent timing requirements， as they need to perform two consumption measurements per second， sign and transmit them. In contrast， EDL meters have to meet rather relaxed timing requirements， a signature might take nearly three minutes to complete without raising any issues.

　　Therefore， ubisys? technologies has extended its C++ template class library CompactECC? with a dedicated implementation of the p192r1 curve. This particular implementation allows for an optimal blend of code size， memory footprint， and execution time， depending on individual application requirements. The library can generally be used with all 8-， 16- and 32-bit controllers for which a C++ or embedded C++ compiler with template support exists. Integration with plain C projects is also possible.