Smash the singular Ciphersuite trait into multiple

This helps identify where the various functionalities are used, or rather, not
used. The `Ciphersuite` trait present in `patches/ciphersuite`, facilitating
the entire FCMP++ tree, only requires the markers _and_ canonical point
decoding. I've opened a PR to upstream such a trait into `group`
(https://github.com/zkcrypto/group/pull/68).

`WrappedGroup` is still justified for as long as `Group::generator` exists.
Moving `::generator()` to its own trait, on an independent structure (upstream)
would be massively appreciated. @tarcieri also wanted to update from
`fn generator()` to `const GENERATOR`, which would encourage further discussion
on https://github.com/zkcrypto/group/issues/32 and
https://github.com/zkcrypto/group/issues/45, which have been stagnant.

The `Id` trait is occasionally used yet really should be first off the chopping
block.

Finally, `WithPreferredHash` is only actually used around a third of the time,
which more than justifies it being a separate trait.

---

Updates `dalek_ff_group::Scalar` to directly re-export
`curve25519_dalek::Scalar`, as without issue. `dalek_ff_group::RistrettoPoint`
also could be replaced with an export of `curve25519_dalek::RistrettoPoint`,
yet the coordinator relies on how we implemented `Hash` on it for the hell of
it so it isn't worth it at this time. `dalek_ff_group::EdwardsPoint` can't be
replaced for an re-export of `curve25519_dalek::SubgroupPoint` as it doesn't
implement `zeroize`, `subtle` traits within a released, non-yanked version.
Relevance to https://github.com/serai-dex/serai/issues/201 and
https://github.com/dalek-cryptography/curve25519-dalek/issues/811#issuecomment-3247732746.

Also updates the `Ristretto` ciphersuite to prefer `Blake2b-512` over
`SHA2-512`. In order to maintain compliance with FROST's IETF standard,
`modular-frost` defines its own ciphersuite for Ristretto which still uses
`SHA2-512`.

patches/ciphersuite/Cargo.toml

@@ -16,13 +16,19 @@ rustdoc-args = ["--cfg", "docsrs"]
 workspace = true
 
 [dependencies]
+std-shims = { path = "../../common/std-shims", version = "0.1.4", default-features = false, optional = true }
+
+zeroize = { version = "1", default-features = false }
 ciphersuite = { path = "../../crypto/ciphersuite", default-features = false }
+
 dalek-ff-group = { path = "../../crypto/dalek-ff-group", default-features = false, optional = true }
 
 [features]
-alloc = ["ciphersuite/alloc"]
+alloc = ["std-shims", "zeroize/alloc", "ciphersuite/alloc", "dalek-ff-group/alloc"]
 std = [
   "alloc",
+  "std-shims/std",
+  "zeroize/std",
   "ciphersuite/std",
   "dalek-ff-group?/std",
 ]

patches/ciphersuite/src/lib.rs

@@ -1,5 +1,33 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
-pub use ciphersuite::*;
+use std_shims::io;
+
+use zeroize::Zeroize;
+pub use ciphersuite::group;
+use group::{*, ff::*, prime::PrimeGroup};
+
+pub trait Ciphersuite: 'static + Send + Sync {
+  type F: PrimeField + PrimeFieldBits + Zeroize;
+  type G: Group<Scalar = Self::F> + GroupOps + PrimeGroup + Zeroize;
+  #[cfg(feature = "alloc")]
+  #[allow(non_snake_case)]
+  fn read_F<R: io::Read>(reader: &mut R) -> io::Result<Self::F>;
+  #[cfg(feature = "alloc")]
+  #[allow(non_snake_case)]
+  fn read_G<R: io::Read>(reader: &mut R) -> io::Result<Self::G>;
+}
+impl<C: ciphersuite::GroupIo> Ciphersuite for C {
+  type F = <C as ciphersuite::WrappedGroup>::F;
+  type G = <C as ciphersuite::WrappedGroup>::G;
+  #[cfg(feature = "alloc")]
+  fn read_F<R: io::Read>(reader: &mut R) -> io::Result<Self::F> {
+    <C as ciphersuite::GroupIo>::read_F(reader)
+  }
+  #[cfg(feature = "alloc")]
+  fn read_G<R: io::Read>(reader: &mut R) -> io::Result<Self::G> {
+    <C as ciphersuite::GroupIo>::read_G(reader)
+}
+}
+
 #[cfg(feature = "ed25519")]
 pub use dalek_ff_group::Ed25519;

patches/dalek-ff-group/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "dalek-ff-group"
-version = "0.4.99"
+version = "0.5.99"
 description = "ff/group bindings around curve25519-dalek"
 license = "MIT"
 repository = "https://github.com/serai-dex/serai/tree/develop/crypto/dalek-ff-group"