SIGMA
===========================


合规建议
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- 重点保护Initiator的信息，则选用SIGMA-I。
- 重点保护Responder的信息，则选用SIGMA-R。


参考资料
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- `SIGMA: the ‘SIGn-and-MAc’ Approach to Authenticated Diffie-Hellman and its Use in the IKE Protocols <https://www.iacr.org/cryptodb/archive/2003/CRYPTO/1495/1495.pdf>`_