Huawei USA Huawei Technologies Co., Ltd. Cisco This document defines a lightweight and secure version of 6LoWPAN Neighbor Discovery for application in low-power and lossy networks. Cryptographically Generated Address and digital signatures are calculated using Elliptic Curve Cryptography, so that the cryptographic operations are suitable for low power devices. An optimal version of this protocol is also specified which supports faster CGA calculation and multi-hop operation. A node computes a Cryptographically Generated Address to be used as a Unique Interface ID, and associate all its Registered Addresses with that Unique Interface ID in place of the EUI-64 that is used in RFC 6775 to uniquely identify the interface of the Registered Address. Once an address is registered with a cryptographic unique ID, only the owner of that ID can modify the state in the 6LR and 6LBR regarding the Registered Address.