mina-signer: make it no-std compatible

The previous commit makes also the repository compatible with Rust
before 1.81. Without the bump up to thiserror = 2, the feature
error_in_core must be activated, and it has been stabilized in 1.81
only.
See rust-lang/rust#103765

Author: dannywillems

signer/src/keypair.rs

@@ -2,7 +2,9 @@
 //!
 //! Definition of secret key, keypairs and related helpers
 
+extern crate alloc;
 use crate::{pubkey::PubKeyError, seckey::SecKeyError, CurvePoint, PubKey, ScalarField, SecKey};
+use alloc::{string::String, vec::Vec};
 use core::fmt;
 use rand::{self, CryptoRng, RngCore};
 use thiserror::Error;

signer/src/lib.rs

@@ -1,6 +1,9 @@
 #![deny(missing_docs)]
 #![doc = include_str!("../README.md")]
+#![no_std]
 
+extern crate alloc;
+use alloc::{vec, vec::Vec};
 use ark_ec::AffineRepr;
 pub use keypair::Keypair;
 pub use mina_curves::pasta::Pallas as CurvePoint;

signer/src/pubkey.rs

@@ -2,7 +2,9 @@
 //!
 //! Definition of public key structure and helpers
 
+extern crate alloc;
 use crate::{BaseField, CurvePoint, ScalarField, SecKey};
+use alloc::{string::String, vec, vec::Vec};
 use ark_ec::{short_weierstrass::Affine, AffineRepr, CurveGroup};
 use ark_ff::{BigInteger, PrimeField, Zero};
 use bs58;

signer/src/schnorr.rs

@@ -4,6 +4,9 @@
 //!
 //! Details: <https://github.com/MinaProtocol/mina/blob/develop/docs/specs/signatures/description.md>
 
+extern crate alloc;
+use alloc::{boxed::Box, string::String};
+
 use crate::{BaseField, CurvePoint, Hashable, Keypair, PubKey, ScalarField, Signature, Signer};
 use ark_ec::{
     AffineRepr, // for generator()

signer/src/seckey.rs

@@ -1,6 +1,8 @@
 //! Secret key structures and helpers
 
+extern crate alloc;
 use crate::ScalarField;
+use alloc::{string::String, vec, vec::Vec};
 use ark_ff::UniformRand;
 use o1_utils::FieldHelpers;
 use rand::{self, CryptoRng, RngCore};