Add no_std support to transcript, dalek-ff-group, ed448, ciphersuite, multiexp, schnorr, and monero-generators

transcript, dalek-ff-group, ed449, and ciphersuite are all usable with no_std
alone. The rest additionally require alloc.

Part of #279.

crypto/ciphersuite/src/ed448.rs

@@ -75,8 +75,7 @@ impl Ciphersuite for Ed448 {
 fn test_ed448() {
   use ff::PrimeField;
 
-  // TODO: Enable once ed448 passes these tests
-  //ff_group_tests::group::test_prime_group_bits::<Point>();
+  ff_group_tests::group::test_prime_group_bits::<_, Point>(&mut rand_core::OsRng);
 
   // Ideally, a test vector from RFC-8032 (not FROST) would be here
   // Unfortunately, the IETF draft doesn't provide any vectors for the derived challenges

crypto/ciphersuite/src/lib.md

@@ -7,3 +7,6 @@ This library, except for the not recommended Ed448 ciphersuite, was
 culminating in commit
 [669d2dbffc1dafb82a09d9419ea182667115df06](https://github.com/serai-dex/serai/tree/669d2dbffc1dafb82a09d9419ea182667115df06).
 Any subsequent changes have not undergone auditing.
+
+This library is usable under no_std. The `alloc` and `std` features enable
+reading from the `io::Read` trait, shimmed by `std-shims` under `alloc`.

crypto/ciphersuite/src/lib.rs

@@ -1,10 +1,10 @@
 #![cfg_attr(docsrs, feature(doc_auto_cfg))]
-#![cfg_attr(not(feature = "std"), no_std)]
 #![doc = include_str!("lib.md")]
+#![cfg_attr(not(feature = "std"), no_std)]
 
 use core::fmt::Debug;
-#[cfg(feature = "std")]
-use std::io::{self, Read};
+#[cfg(any(feature = "alloc", feature = "std"))]
+use std_shims::io::{self, Read};
 
 use rand_core::{RngCore, CryptoRng};
 
@@ -20,7 +20,7 @@ use group::{
   Group, GroupOps,
   prime::PrimeGroup,
 };
-#[cfg(feature = "std")]
+#[cfg(any(feature = "alloc", feature = "std"))]
 use group::GroupEncoding;
 
 #[cfg(feature = "dalek")]
@@ -85,7 +85,7 @@ pub trait Ciphersuite:
   }
 
   /// Read a canonical scalar from something implementing std::io::Read.
-  #[cfg(feature = "std")]
+  #[cfg(any(feature = "alloc", feature = "std"))]
   #[allow(non_snake_case)]
   fn read_F<R: Read>(reader: &mut R) -> io::Result<Self::F> {
     let mut encoding = <Self::F as PrimeField>::Repr::default();
@@ -99,7 +99,7 @@ pub trait Ciphersuite:
   }
 
   /// Read a canonical point from something implementing std::io::Read.
-  #[cfg(feature = "std")]
+  #[cfg(any(feature = "alloc", feature = "std"))]
   #[allow(non_snake_case)]
   fn read_G<R: Read>(reader: &mut R) -> io::Result<Self::G> {
     let mut encoding = <Self::G as GroupEncoding>::Repr::default();