Adding taptree_of_horror example.

Adding bitcoin_hashes as dev dependency.

Author: miketwenty1

Cargo.toml

@@ -1,12 +1,14 @@
 [package]
 name = "miniscript"
 version = "12.2.0"
-authors = ["Andrew Poelstra <[email protected]>, Sanket Kanjalkar <[email protected]>"]
+authors = [
+    "Andrew Poelstra <[email protected]>, Sanket Kanjalkar <[email protected]>",
+]
 license = "CC0-1.0"
 homepage = "https://github.com/rust-bitcoin/rust-miniscript/"
 repository = "https://github.com/rust-bitcoin/rust-miniscript/"
 description = "Miniscript: a subset of Bitcoin Script designed for analysis"
-keywords = [ "crypto", "bitcoin", "miniscript", "script" ]
+keywords = ["crypto", "bitcoin", "miniscript", "script"]
 readme = "README.md"
 edition = "2021"
 rust-version = "1.63.0"
@@ -32,7 +34,8 @@ actual-serde = { package = "serde", version = "1.0.103", optional = true }
 [dev-dependencies]
 serde_test = "1.0.147"
 bitcoin = { version = "0.32.0", features = ["base64"] }
-secp256k1 = {version = "0.29.0", features = ["rand-std"]}
+secp256k1 = { version = "0.29.0", features = ["rand-std"] }
+bitcoin_hashes = "0.14.0"
 
 [[example]]
 name = "htlc"
@@ -56,7 +59,7 @@ required-features = ["std"]
 
 [[example]]
 name = "taproot"
-required-features = ["compiler","std"]
+required-features = ["compiler", "std"]
 
 [[example]]
 name = "psbt_sign_finalize"
@@ -66,6 +69,12 @@ required-features = ["std", "base64"]
 name = "big"
 required-features = ["std", "base64", "compiler"]
 
+[[example]]
+name = "taptree_of_horror"
+path = "examples/taptree_of_horror/taptree_of_horror.rs"
+required-features = ["compiler"]
+
+
 [workspace]
 members = ["fuzz"]
 exclude = ["embedded", "bitcoind-tests"]

examples/taptree_of_horror/README.md

@@ -0,0 +1,20 @@
+# Taptree of Horror Example
+
+### Running this example:
+- `cargo run --example taptree_of_horror --features "compiler"`
+
+### Originally based on the TABConf 6, CTB. 
+The challenge can be found here:
+- https://tabctb.com/six
+- https://tabctb.com/six/thebeginning/thetree/grim/iacceptyourterms.html
+
+### This example demonstrates:
+- Providing multiple extended private key (xpriv) descriptors for sample personas.
+- Creating a policy using logical 'and/or' conditions with preimages and signatures and timelocks.
+- Structuring a Taproot tree (taptree) with an internal key into logical branches and leaves based on the policy.
+- Implementing nine complex tapleaves within the taptree.
+- Building a spending transaction that signs and satisfies one of the tapleaves using signatures, preimages and a timelock.
+
+### Helpful Graphic to visualize using Excalidraw
+![taptree_of_horror](./taptree_of_horror.png)
+

examples/taptree_of_horror/helper_fns.rs

@@ -0,0 +1,59 @@
+use std::str::FromStr;
+
+use bitcoin::{
+    bip32::{DerivationPath, Xpriv},
+    hashes::{ripemd160, sha256},
+};
+use bitcoin_hashes::Hash;
+use miniscript::{descriptor::DescriptorSecretKey, ToPublicKey};
+use secp256k1::Secp256k1;
+
+pub fn produce_grim_hash(secret: &str) -> (sha256::Hash, ripemd160::Hash) {
+    let mut hash_holder = sha256::Hash::hash(secret.as_bytes());
+    for _i in 0..5 {
+        hash_holder = sha256::Hash::hash(hash_holder.as_byte_array());
+        //println!("{} hash: {}", i, hash_holder);
+    }
+
+    let ripemd_160_final = ripemd160::Hash::hash(hash_holder.as_byte_array());
+    (hash_holder, ripemd_160_final)
+}
+
+pub fn produce_kelly_hash(secret: &str) -> (sha256::Hash, sha256::Hash) {
+    let prepreimage: Vec<u8> = secret.as_bytes().to_vec();
+    let preimage_256_hash = sha256::Hash::hash(&prepreimage);
+    let result256_final = sha256::Hash::hash(&preimage_256_hash.to_byte_array());
+    (preimage_256_hash, result256_final)
+}
+
+pub fn produce_key_pairs(
+    desc: DescriptorSecretKey,
+    secp: &Secp256k1<secp256k1::All>,
+    derivation_without_index: &str,
+    _alias: &str,
+) -> (Vec<bitcoin::PublicKey>, Vec<Xpriv>) {
+    let mut pks = Vec::new();
+    let mut prvs = Vec::new();
+
+    let xprv = match &desc {
+        DescriptorSecretKey::XPrv(xpriv) => xpriv,
+        _ => panic!("not an xpriv"),
+    };
+
+    for i in 0..9 {
+        let pk = desc
+            .to_public(secp)
+            .unwrap()
+            .at_derivation_index(i)
+            .unwrap()
+            .to_public_key();
+
+        let derivation_with_index = format!("{}/{}", derivation_without_index, i);
+        let derivation_path = DerivationPath::from_str(&derivation_with_index).unwrap();
+        let derived_xpriv: Xpriv = xprv.xkey.derive_priv(secp, &derivation_path).unwrap();
+
+        pks.insert(i.try_into().unwrap(), pk);
+        prvs.insert(i.try_into().unwrap(), derived_xpriv);
+    }
+    (pks, prvs)
+}