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/multiexp/Cargo.toml

@@ -15,18 +15,24 @@ rustdoc-args = ["--cfg", "docsrs"]
 [dependencies]
 rustversion = "1"
 
+std-shims = { path = "../../common/std-shims", version = "0.1", default-features = false }
+
 zeroize = { version = "^1.5", features = ["zeroize_derive"] }
 
-ff = "0.13"
-group = "0.13"
+ff = { version = "0.13", default-features = false, features = ["bits"] }
+group = { version = "0.13", default-features = false }
 
-rand_core = { version = "0.6", optional = true }
+rand_core = { version = "0.6", default-features = false, optional = true }
 
 [dev-dependencies]
-rand_core = "0.6"
+rand_core = { version = "0.6", features = ["std"] }
 
-k256 = { version = "^0.13.1", default-features = false, features = ["std", "arithmetic", "bits"] }
+k256 = { version = "^0.13.1", default-features = false, features = ["arithmetic", "bits"] }
 dalek-ff-group = { path = "../dalek-ff-group" }
 
 [features]
+std = ["std-shims/std"]
+
 batch = ["rand_core"]
+
+default = ["std"]

crypto/multiexp/README.md

@@ -3,10 +3,14 @@
 A multiexp implementation for ff/group implementing Straus and Pippenger. A
 batch verification API is also available via the "batch" feature, which enables
 secure multiexponentation batch verification given a series of values which
-should sum to 0, identifying which doesn't via binary search if they don't.
+should sum to the identity, identifying which doesn't via binary search if they
+don't.
 
 This library was
 [audited by Cypher Stack in March 2023](https://github.com/serai-dex/serai/raw/e1bb2c191b7123fd260d008e31656d090d559d21/audits/Cypher%20Stack%20crypto%20March%202023/Audit.pdf),
 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, via alloc, when the default features are
+disabled.

crypto/multiexp/src/batch.rs

@@ -1,3 +1,5 @@
+use std_shims::vec::Vec;
+
 use rand_core::{RngCore, CryptoRng};
 
 use zeroize::{Zeroize, Zeroizing};

crypto/multiexp/src/lib.rs

@@ -1,7 +1,12 @@
 #![cfg_attr(docsrs, feature(doc_auto_cfg))]
 #![doc = include_str!("../README.md")]
+#![cfg_attr(not(feature = "std"), no_std)]
 
 use core::ops::DerefMut;
+#[cfg(not(feature = "std"))]
+#[macro_use]
+extern crate alloc;
+use std_shims::vec::Vec;
 
 use zeroize::Zeroize;
 

crypto/multiexp/src/straus.rs

@@ -1,3 +1,5 @@
+use std_shims::vec::Vec;
+
 use zeroize::Zeroize;
 
 use ff::PrimeFieldBits;