Improve the public API

We created the `crypto` crate as a container for cryptography modules
with the idea that it may be split out into a separate crate. There is
no reason for users of the lib to know about this module. Also, we have
two `taproot` modules, one in `crypto` and one at the crate root, this
makes for un-ergonomic usage of the lib.

Improve the public API by doing:

- Make the `crypto` module private (`pub(crate)`).
- Re-export `crypto::taproot::Signature` (and `Error`) from
  `crate::taproot`

bitcoin/examples/taproot-psbt.rs

@@ -81,15 +81,12 @@ use std::str::FromStr;
 use bitcoin::bip32::{ChildNumber, DerivationPath, ExtendedPrivKey, ExtendedPubKey, Fingerprint};
 use bitcoin::consensus::encode;
 use bitcoin::constants::COIN_VALUE;
-use bitcoin::crypto::taproot;
 use bitcoin::key::{TapTweak, XOnlyPublicKey};
 use bitcoin::opcodes::all::{OP_CHECKSIG, OP_CLTV, OP_DROP};
 use bitcoin::psbt::{self, Input, Output, Psbt, PsbtSighashType};
 use bitcoin::secp256k1::Secp256k1;
-use bitcoin::sighash::{self, TapSighashType, SighashCache};
-use bitcoin::taproot::{
-    LeafVersion, TapLeafHash, TapSighash, TaprootBuilder, TaprootSpendInfo,
-};
+use bitcoin::sighash::{self, SighashCache, TapSighash, TapSighashType};
+use bitcoin::taproot::{self, LeafVersion, TapLeafHash, TaprootBuilder, TaprootSpendInfo};
 use bitcoin::{
     absolute, script, Address, Amount, Network, OutPoint, ScriptBuf, Transaction, TxIn, TxOut,  Witness,
 };

bitcoin/src/blockdata/transaction.rs

@@ -589,8 +589,8 @@ impl<E> EncodeSigningDataResult<E> {
     ///
     /// ```rust
     /// # use bitcoin::consensus::deserialize;
+    /// # use bitcoin::sighash::{LegacySighash, SighashCache};
     /// # use bitcoin::Transaction;
-    /// # use bitcoin::crypto::sighash::{LegacySighash, SighashCache};
     /// # use bitcoin_hashes::{Hash, hex::FromHex};
     /// # let mut writer = LegacySighash::engine();
     /// # let input_index = 0;

bitcoin/src/crypto/key.rs

@@ -578,7 +578,7 @@ pub type UntweakedKeyPair = KeyPair;
 /// # Examples
 /// ```
 /// # #[cfg(feature = "rand-std")] {
-/// # use bitcoin::crypto::key::{KeyPair, TweakedKeyPair, TweakedPublicKey};
+/// # use bitcoin::key::{KeyPair, TweakedKeyPair, TweakedPublicKey};
 /// # use bitcoin::secp256k1::{rand, Secp256k1};
 /// # let secp = Secp256k1::new();
 /// # let keypair = TweakedKeyPair::dangerous_assume_tweaked(KeyPair::new(&secp, &mut rand::thread_rng()));

bitcoin/src/crypto/mod.rs

@@ -9,4 +9,5 @@
 pub mod ecdsa;
 pub mod key;
 pub mod sighash;
-pub mod taproot;
+// Contents re-exported in `bitcoin::taproot`.
+pub(crate) mod taproot;

bitcoin/src/lib.rs

@@ -92,7 +92,8 @@ pub mod bip158;
 pub mod bip32;
 pub mod blockdata;
 pub mod consensus;
-pub mod crypto;
+// Private until we either make this a crate or flatten it - still to be decided.
+pub(crate) mod crypto;
 pub mod error;
 pub mod hash_types;
 pub mod merkle_tree;
@@ -127,7 +128,7 @@ pub use crate::blockdata::witness::{self, Witness};
 pub use crate::blockdata::{constants, opcodes};
 pub use crate::consensus::encode::VarInt;
 pub use crate::crypto::key::{self, PrivateKey, PublicKey};
-pub use crate::crypto::sighash;
+pub use crate::crypto::{ecdsa, sighash};
 pub use crate::error::Error;
 pub use crate::hash_types::{Txid, Wtxid, BlockHash, PubkeyHash,  ScriptHash, WPubkeyHash, WScriptHash};
 pub use crate::merkle_tree::MerkleBlock;

bitcoin/src/taproot.rs

@@ -13,12 +13,13 @@ use bitcoin_internals::write_err;
 use secp256k1::{self, Scalar, Secp256k1};
 
 use crate::consensus::Encodable;
-use crate::crypto::key::{TapTweak, TweakedPublicKey, UntweakedPublicKey, XOnlyPublicKey};
 use crate::hashes::{sha256t_hash_newtype, Hash, HashEngine};
+use crate::crypto::key::{TapTweak, TweakedPublicKey, UntweakedPublicKey, XOnlyPublicKey};
 use crate::prelude::*;
 use crate::{io, Script, ScriptBuf};
 
-pub use crate::crypto::sighash::{TapSighash, TapSighashTag};
+// Re-export these so downstream only has to use one `taproot` module.
+pub use crate::crypto::taproot::{Signature, Error};
 
 /// The SHA-256 midstate value for the TapLeaf hash.
 const MIDSTATE_TAPLEAF: [u8; 32] = [
@@ -1133,6 +1134,7 @@ mod test {
     use crate::hashes::hex::FromHex;
     use crate::hashes::sha256t::Tag;
     use crate::hashes::{sha256, Hash, HashEngine};
+    use crate::sighash::{TapSighash, TapSighashTag};
     use crate::{Address, Network};
     extern crate serde_json;
 

bitcoin/tests/serde.rs

@@ -30,16 +30,15 @@ use bitcoin::bip32::{ChildNumber, ExtendedPrivKey, ExtendedPubKey, KeySource};
 use bitcoin::blockdata::locktime::{absolute, relative};
 use bitcoin::blockdata::witness::Witness;
 use bitcoin::consensus::encode::deserialize;
-use bitcoin::crypto::key::UntweakedPublicKey;
-use bitcoin::crypto::{ecdsa, taproot};
 use bitcoin::hashes::hex::FromHex;
 use bitcoin::hashes::{hash160, ripemd160, sha256, sha256d, Hash};
+use bitcoin::key::UntweakedPublicKey;
 use bitcoin::psbt::raw::{self, Key, Pair, ProprietaryKey};
 use bitcoin::psbt::{Input, Output, Psbt, PsbtSighashType};
 use bitcoin::sighash::{EcdsaSighashType, TapSighashType};
-use bitcoin::taproot::{ControlBlock, LeafVersion, TaprootBuilder, TaprootSpendInfo};
+use bitcoin::taproot::{self, ControlBlock, LeafVersion, TaprootBuilder, TaprootSpendInfo};
 use bitcoin::{
-    Address, Block, Network, OutPoint, PrivateKey, PublicKey, ScriptBuf, Sequence, Target,
+    ecdsa, Address, Block, Network, OutPoint, PrivateKey, PublicKey, ScriptBuf, Sequence, Target,
     Transaction, TxIn, TxOut, Txid, Work,
 };
 use secp256k1::Secp256k1;