add functions to support nova repo #44
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chaosma
commented
May 21, 2023
chaosma
commented
- add hash_to_curve function
- add from_slice function
- fix minor issue of ysign in from_bytes
| impl [< $name Compressed >] { | ||
| pub fn from_slice(slice: &[u8]) -> Result<Self, &'static str> { | ||
| if slice.len() != [< $name _COMPRESSED_SIZE >] { | ||
| return Err("Slice length not match"); | ||
| } | ||
| let mut c = [0u8; [< $name _COMPRESSED_SIZE >]]; | ||
| c.copy_from_slice(slice); | ||
| Ok(Self(c)) | ||
| } | ||
| } | ||
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What's the usecase for this function? I feel one can do this already by compressed.as_mut().copy_from_slice(slice), and copy_from_slice will panic if the length is uneuqal.
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In nova, the Group trait requires to define decompressed method to convert [u8;32] to G1Compressed. I didn't find there is a public method that allow me to do this conversion, so I added from_slice. What is compressed defined in this code?
| use ff::{FromUniformBytes, PrimeField}; | ||
| use static_assertions::const_assert; | ||
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| // TODO: use simplified swu algorithm |
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So to use simplified swu method, we need to find the isogeny parameters right? Is there a deterministic script to do that? (this one might be it https://github.com/cfrg/draft-irtf-cfrg-hash-to-curve/blob/main/poc/iso_values.sage?)
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Yes, we need first convert A=0 case to A*B != 0 curve before using simplified swu. en... Let me take a look at this code.
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I have a complete script to find Z and the SWU isogenies here as well: https://github.com/mratsim/constantine/blob/d996ccd/sage/derive_hash_to_curve.sage#L145-L275
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is this PR overriden by #47? |
