Couple rand core and zeroize (#171)

## What?

1) Couple `rand_core` and `zeroize` versions with re-exports from
`elliptic_curve` (and re-export them).
2) Move `sha2` to private dependencies.

## Why?

* Re-exporting `rand_core` and `zeroize` crates makes them more
accessible for users of the library (so user of `elastic_elgamal`
doesn't need to check which version of `rand_core`/`zeroize` is
compatible).
* This ensures that `elastic_elgamal` uses the same version of
`rand_core` and `zeroize` as `elliptic-curve` crate.
* Should decrease maintenance burden.

Author: dobo90

Cargo.lock

@@ -26,10 +26,7 @@ rustdoc-args = ["--cfg", "docsrs"]
 
 [dependencies]
 # Public dependencies (present in public API of the crate).
-elliptic-curve = { version = "=0.14.0-rc.16", features = ["sec1"] }
-rand_core = { version = "0.9.3", default-features = false }
-zeroize = { version = "1.8.2", default-features = false, features = ["alloc"] }
-sha2 = { version = "=0.11.0-rc.2", default-features = false }
+elliptic-curve = { version = "=0.14.0-rc.16", features = ["alloc", "sec1"] }
 
 # Enables `Serialize` / `Deserialize` implementation for most types in the crate.
 serde = { version = "1.0", default-features = false, features = ["derive", "alloc"], optional = true }
@@ -39,6 +36,7 @@ base64ct = { version = "1.8", default-features = false, features = ["alloc"] }
 hashbrown = { version = "0.16.0", optional = true }
 merlin = { version = "3.0.0", default-features = false }
 rand_chacha = { version = "0.9.0", default-features = false }
+sha2 = { version = "=0.11.0-rc.2", default-features = false }
 subtle = { version = "2.6.1", default-features = false }
 
 # Crypto backend to support Curve25519 prime subgroup and Ristretto255 group;

Cargo.toml

@@ -6,9 +6,9 @@ use elastic_elgamal::{
     Keypair, ProofOfPossession,
     group::{Curve25519Subgroup, Generic, Group, Ristretto},
 };
+use elliptic_curve::rand_core::SeedableRng;
 use merlin::Transcript;
 use rand_chacha::ChaChaRng;
-use rand_core::SeedableRng;
 
 type K256 = Generic<k256::Secp256k1>;
 

benches/sharing.rs

@@ -31,7 +31,7 @@ fn upgrade_point(x: bulletproofs_curve::RistrettoPoint) -> curve25519_dalek::Ris
 #[derive(Debug)]
 struct CompatRng<R>(R);
 
-impl<R: rand_core::RngCore> bulletproofs_rand_core::RngCore for CompatRng<R> {
+impl<R: elliptic_curve::rand_core::RngCore> bulletproofs_rand_core::RngCore for CompatRng<R> {
     fn next_u32(&mut self) -> u32 {
         self.0.next_u32()
     }
@@ -50,7 +50,7 @@ impl<R: rand_core::RngCore> bulletproofs_rand_core::RngCore for CompatRng<R> {
     }
 }
 
-impl<R: rand_core::CryptoRng> bulletproofs_rand_core::CryptoRng for CompatRng<R> {}
+impl<R: elliptic_curve::rand_core::CryptoRng> bulletproofs_rand_core::CryptoRng for CompatRng<R> {}
 
 fn main() {
     let mut rng = rand::rng();

examples/equivalence.rs

@@ -15,11 +15,11 @@ use elastic_elgamal::{
     group::{Generic, Group, Ristretto},
     sharing::{ActiveParticipant, Dealer, Params, PublicKeySet},
 };
+use elliptic_curve::rand_core::{CryptoRng, RngCore};
 use rand::{
     Rng,
     seq::{IndexedMutRandom, IteratorRandom},
 };
-use rand_core::{CryptoRng, RngCore};
 
 type K256 = Generic<k256::Secp256k1>;
 

examples/voting.rs

@@ -2,11 +2,13 @@
 
 use core::{fmt, iter, ops};
 
+use elliptic_curve::{
+    rand_core::{CryptoRng, RngCore},
+    zeroize::Zeroizing,
+};
 use merlin::Transcript;
-use rand_core::{CryptoRng, RngCore};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize, de::DeserializeOwned};
-use zeroize::Zeroizing;
 
 use crate::{
     Ciphertext, CiphertextWithValue, LogEqualityProof, PublicKey, RingProof, RingProofBuilder,

src/app/choice.rs

@@ -2,8 +2,8 @@
 
 use core::fmt;
 
+use elliptic_curve::rand_core::{CryptoRng, RngCore};
 use merlin::Transcript;
-use rand_core::{CryptoRng, RngCore};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 

src/app/quadratic_voting.rs

@@ -1,7 +1,7 @@
 //! Verifiable decryption.
 
+use elliptic_curve::rand_core::{CryptoRng, RngCore};
 use merlin::Transcript;
-use rand_core::{CryptoRng, RngCore};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 

src/decryption.rs

@@ -98,11 +98,13 @@
 
 use core::fmt;
 
-use rand_core::{CryptoRng, RngCore};
+use elliptic_curve::{
+    rand_core::{CryptoRng, RngCore},
+    zeroize::Zeroizing,
+};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 use sha2::{Digest, Sha256};
-use zeroize::Zeroizing;
 
 #[cfg(feature = "serde")]
 use crate::serde::{ElementHelper, VecHelper};

src/dkg.rs

@@ -2,10 +2,12 @@
 
 use core::{fmt, marker::PhantomData, ops};
 
-use rand_core::{CryptoRng, RngCore};
+use elliptic_curve::{
+    rand_core::{CryptoRng, RngCore},
+    zeroize::{Zeroize, Zeroizing},
+};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
-use zeroize::{Zeroize, Zeroizing};
 
 #[cfg(feature = "serde")]
 use crate::serde::ElementHelper;