Hi Thom,
 
Hi Guilin and Valery,
 


Op 7 apr 2026, om 11:12 heeft Wang Guilin 
<[email protected]> het volgende geschreven:
 
In addition, beside using ML-KEM to replace ML-DSA for authentication in IKEv2, 
we also noticed that some other KEMs could be good candidates as well. For 
example, Classic McEliece has public key sizes from 260KB to 1.36 MB, which is 
huge compared to ML-KEM. However, the ciphertext sizes are just 96-208 bytes, 
very short. Therefore, in the case two entities need to authentication with 
each other frequently,  Classic McEliece could  be a good choice to save 
communication overhead, by assuming that each side can store public key or 
certificate of the other side. If a few MB storage is not an issue, using 
Classic McEliece as KEM based authentication may be even practical for IoT 
devices with constrained capability, but only communicating with fixed parties. 

Table 6 in [1] gives the exact sizes of Classic McEliece variants.
 
I think that the use of Classic McEliece to avoid transmission suits IKEv2 
well, since it supports some “Certificate” formats such as the hash-and-url 
scheme that very naturally work for this out-of-band distribution of public 
keys.
 
Of course this mechanism will also be useful for UOV-style schemes that have 
very large public keys but small signatures.
 
         Hash-and-URL was indeed considered while writing the draft as a way to 
avoid sending large data. But with pre-provisioned certificates the “URL” part 
becomes unnecessary
         (as opposed to the cashed certificates). RFC 7296 is unclear whether 
this part can be omitted at all, but this can be easily clarified as a corner 
case
         for the Hash-and-URL encoding, when only hash is present. 
Alternatively, some “dummy” URL can be included, but this looks like a hack.
 
          Regards,
         Valery.
 
Cheers,
Thom
 
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