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clarifications about hash-based digital sigs 

[Imported from Trac: page OneHundredYearCryptography, version 17]
davidsarah 2011-12-21 22:25:13 +00:00
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OneHundredYearCryptography.md

@ -31,16 +31,16 @@ David-Sarah has proposed to use hash-based digital signatures.
Zooko posted ["back of the envelope" performance constraints](https://tahoe-lafs.org/pipermail/tahoe-dev/2011-February/006133.html). Bottom-line: you get 30 million ARM instructions to implement one complete digital signature verification.
Julian Wälde has [posted an actual implementation](http://tahoe-lafs.org/pipermail/tahoe-dev/2011-March/006237.html) of hash-based digital signatures! Exciting fact: his implementation meets Zooko's performance criterion!
Julian Wälde has [posted an actual implementation](http://tahoe-lafs.org/pipermail/tahoe-dev/2011-March/006237.html) of (stateful) hash-based digital signatures! Exciting fact: his implementation meets Zooko's performance criterion!
Brian and David-Sarah wrote [a simulator]source:trunk/misc/simulators/hashbasedsig.py or two to explore performance trade-offs in hash-based signature parameters. The output of one run with the following parameters is this:
Brian and David-Sarah wrote [a simulator]source:trunk/misc/simulators/hashbasedsig.py or two to explore performance trade-offs in (stateless) hash-based signature parameters. The output of one run with the following parameters is this (note that the signing times include regeneration of per-message signing keys from a small long-term private key):
```
# range of hash output lengths
range_L_hash = [128]
lg_M = 53 # lg(required number of signatures before losing security)
limit_bytes = 20000 # limit on signature length
limit_bytes = 20000 # limit on signature length
limit_cost = 500 # limit on Mcycles_Sig + weight_ver*Mcycles_ver
weight_ver = 1 # how important verification cost is relative to signature cost
# (note: setting this too high will just exclude useful candidates)