Move the SerializedSignature to cryto module

diff --git a/bitcoin/src/crypto/taproot.rs b/bitcoin/src/crypto/taproot.rs
index 373d7d35..2f7dd85d 100644
--- a/bitcoin/src/crypto/taproot.rs
+++ b/bitcoin/src/crypto/taproot.rs
@@ -4,8 +4,9 @@
 //!
 //! This module provides Taproot signatures used by Bitcoin that can be roundtrip (de)serialized.
 
+use core::borrow::Borrow;
 use core::convert::Infallible;
-use core::fmt;
+use core::{fmt, ops};
 
 #[cfg(feature = "arbitrary")]
 use arbitrary::{Arbitrary, Unstructured};
@@ -15,7 +16,10 @@ use io::Write;
 
 use crate::prelude::Vec;
 use crate::sighash::{InvalidSighashTypeError, TapSighashType};
-use crate::taproot::serialized_signature::{self, SerializedSignature};
+
+pub use self::into_iter::IntoIter;
+
+const MAX_LEN: usize = 65; // 64 for sig, 1B sighash flag
 
 /// A BIP-0340-0341 serialized Taproot signature with the corresponding hash type.
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
@@ -49,7 +53,7 @@ impl Signature {
     /// This returns a type with an API very similar to that of `Box<[u8]>`.
     /// You can get a slice from it using deref coercions or turn it into an iterator.
     pub fn serialize(self) -> SerializedSignature {
-        let mut buf = [0; serialized_signature::MAX_LEN];
+        let mut buf = [0; MAX_LEN];
         let ser_sig = self.signature.to_byte_array();
         buf[..64].copy_from_slice(&ser_sig);
         let len = if self.sighash_type == TapSighashType::Default {
@@ -82,6 +86,255 @@ impl Signature {
     }
 }
 
+/// A serialized Taproot Signature
+///
+/// Serialized Taproot signatures have the issue that they can have different lengths.
+/// We want to avoid using `Vec` since that would require allocations making the code slower and
+/// unable to run on platforms without an allocator.
+#[derive(Copy, Clone)]
+pub struct SerializedSignature {
+    data: [u8; MAX_LEN],
+    len: usize,
+}
+
+impl SerializedSignature {
+    /// Constructs new `SerializedSignature` from data and length.
+    ///
+    /// # Panics
+    ///
+    /// If `len` > `MAX_LEN`
+    #[inline]
+    pub(crate) fn from_raw_parts(data: [u8; MAX_LEN], len: usize) -> Self {
+        assert!(len <= MAX_LEN, "attempt to set length to {} but the maximum is {}", len, MAX_LEN);
+        Self { data, len }
+    }
+
+    /// Get the len of the used data.
+    // `len` is never 0, so `is_empty` would always return `false`.
+    #[allow(clippy::len_without_is_empty)]
+    #[inline]
+    pub fn len(&self) -> usize { self.len }
+
+    /// Set the length of the object.
+    #[inline]
+    pub(crate) fn set_len_unchecked(&mut self, len: usize) { self.len = len; }
+
+    /// Convert the serialized signature into the Signature struct.
+    /// (This deserializes it)
+    #[inline]
+    pub fn to_signature(self) -> Result<Signature, SigFromSliceError> {
+        Signature::from_slice(&self)
+    }
+
+    /// Constructs a new SerializedSignature from a Signature.
+    /// (this serializes it)
+    #[inline]
+    pub fn from_signature(sig: Signature) -> Self { sig.serialize() }
+
+    /// Writes this serialized signature to a `writer`.
+    #[inline]
+    pub fn write_to<W: Write + ?Sized>(&self, writer: &mut W) -> Result<(), io::Error> {
+        writer.write_all(self)
+    }
+}
+
+impl fmt::Debug for SerializedSignature {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { fmt::Display::fmt(self, f) }
+}
+
+impl fmt::Display for SerializedSignature {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        hex::fmt_hex_exact!(f, MAX_LEN, self, hex::Case::Lower)
+    }
+}
+
+impl PartialEq for SerializedSignature {
+    #[inline]
+    fn eq(&self, other: &Self) -> bool { **self == **other }
+}
+
+impl PartialEq<[u8]> for SerializedSignature {
+    #[inline]
+    fn eq(&self, other: &[u8]) -> bool { **self == *other }
+}
+
+impl PartialEq<SerializedSignature> for [u8] {
+    #[inline]
+    fn eq(&self, other: &SerializedSignature) -> bool { *self == **other }
+}
+
+impl PartialOrd for SerializedSignature {
+    fn partial_cmp(&self, other: &Self) -> Option<core::cmp::Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for SerializedSignature {
+    fn cmp(&self, other: &Self) -> core::cmp::Ordering { (**self).cmp(&**other) }
+}
+
+impl PartialOrd<[u8]> for SerializedSignature {
+    fn partial_cmp(&self, other: &[u8]) -> Option<core::cmp::Ordering> {
+        (**self).partial_cmp(other)
+    }
+}
+
+impl PartialOrd<SerializedSignature> for [u8] {
+    fn partial_cmp(&self, other: &SerializedSignature) -> Option<core::cmp::Ordering> {
+        self.partial_cmp(&**other)
+    }
+}
+
+impl core::hash::Hash for SerializedSignature {
+    fn hash<H: core::hash::Hasher>(&self, state: &mut H) { (**self).hash(state) }
+}
+
+impl AsRef<[u8]> for SerializedSignature {
+    #[inline]
+    fn as_ref(&self) -> &[u8] { self }
+}
+
+impl Borrow<[u8]> for SerializedSignature {
+    #[inline]
+    fn borrow(&self) -> &[u8] { self }
+}
+
+impl ops::Deref for SerializedSignature {
+    type Target = [u8];
+
+    #[inline]
+    fn deref(&self) -> &[u8] { &self.data[..self.len] }
+}
+
+impl Eq for SerializedSignature {}
+
+impl IntoIterator for SerializedSignature {
+    type IntoIter = IntoIter;
+    type Item = u8;
+
+    #[inline]
+    fn into_iter(self) -> Self::IntoIter { IntoIter::new(self) }
+}
+
+impl<'a> IntoIterator for &'a SerializedSignature {
+    type IntoIter = core::slice::Iter<'a, u8>;
+    type Item = &'a u8;
+
+    #[inline]
+    fn into_iter(self) -> Self::IntoIter { self.iter() }
+}
+
+impl From<Signature> for SerializedSignature {
+    fn from(value: Signature) -> Self { Self::from_signature(value) }
+}
+
+impl<'a> From<&'a Signature> for SerializedSignature {
+    fn from(value: &'a Signature) -> Self { Self::from_signature(*value) }
+}
+
+impl TryFrom<SerializedSignature> for Signature {
+    type Error = SigFromSliceError;
+
+    fn try_from(value: SerializedSignature) -> Result<Self, Self::Error> { value.to_signature() }
+}
+
+impl<'a> TryFrom<&'a SerializedSignature> for Signature {
+    type Error = SigFromSliceError;
+
+    fn try_from(value: &'a SerializedSignature) -> Result<Self, Self::Error> {
+        value.to_signature()
+    }
+}
+
+
+/// Separate mod to prevent outside code from accidentally breaking invariants.
+mod into_iter {
+    use super::*;
+
+    /// Owned iterator over the bytes of [`SerializedSignature`]
+    ///
+    /// Created by [`IntoIterator::into_iter`] method.
+    // allowed because of https://github.com/rust-lang/rust/issues/98348
+    #[allow(missing_copy_implementations)]
+    #[derive(Debug, Clone)]
+    pub struct IntoIter {
+        signature: SerializedSignature,
+        // invariant: pos <= signature.len()
+        pos: usize,
+    }
+
+    impl IntoIter {
+        #[inline]
+        pub(crate) fn new(signature: SerializedSignature) -> Self {
+            Self {
+                signature,
+                // for all unsigned n: 0 <= n
+                pos: 0,
+            }
+        }
+
+        /// Returns the remaining bytes as a slice.
+        ///
+        /// This method is analogous to [`core::slice::Iter::as_slice`].
+        #[inline]
+        pub fn as_slice(&self) -> &[u8] { &self.signature[self.pos..] }
+    }
+
+    impl Iterator for IntoIter {
+        type Item = u8;
+
+        #[inline]
+        fn next(&mut self) -> Option<Self::Item> {
+            let byte = *self.signature.get(self.pos)?;
+            // can't overflow or break invariant because if pos is too large we return early
+            self.pos += 1;
+            Some(byte)
+        }
+
+        #[inline]
+        fn size_hint(&self) -> (usize, Option<usize>) {
+            // can't overflow thanks to the invariant
+            let len = self.signature.len() - self.pos;
+            (len, Some(len))
+        }
+
+        // override for speed
+        #[inline]
+        fn nth(&mut self, n: usize) -> Option<Self::Item> {
+            if n >= self.len() {
+                // upholds invariant because the values will be equal
+                self.pos = self.signature.len();
+                None
+            } else {
+                // if n < signature.len() - self.pos then n + self.pos < signature.len() which neither
+                // overflows nor breaks the invariant
+                self.pos += n;
+                self.next()
+            }
+        }
+    }
+
+    impl ExactSizeIterator for IntoIter {}
+
+    impl core::iter::FusedIterator for IntoIter {}
+
+    impl DoubleEndedIterator for IntoIter {
+        #[inline]
+        fn next_back(&mut self) -> Option<Self::Item> {
+            if self.pos == self.signature.len() {
+                return None;
+            }
+
+            // if len is 0 then pos is also 0 thanks to the invariant so we would return before we
+            // reach this
+            let new_len = self.signature.len() - 1;
+            let byte = self.signature[new_len];
+            self.signature.set_len_unchecked(new_len);
+            Some(byte)
+        }
+    }
+}
+
 /// An error constructing a [`taproot::Signature`] from a byte slice.
 ///
 /// [`taproot::Signature`]: crate::crypto::taproot::Signature
@@ -144,3 +397,39 @@ impl<'a> Arbitrary<'a> for Signature {
         })
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::{SerializedSignature, MAX_LEN};
+
+    #[test]
+    fn iterator_ops_are_homomorphic() {
+        let mut fake_signature_data = [0; MAX_LEN];
+        for (i, byte) in fake_signature_data.iter_mut().enumerate() {
+            *byte = i as u8;
+        }
+
+        let fake_signature = SerializedSignature { data: fake_signature_data, len: MAX_LEN };
+
+        let mut iter1 = fake_signature.into_iter();
+        let mut iter2 = fake_signature.iter();
+
+        // while let so we can compare size_hint and as_slice
+        while let (Some(a), Some(b)) = (iter1.next(), iter2.next()) {
+            assert_eq!(a, *b);
+            assert_eq!(iter1.size_hint(), iter2.size_hint());
+            assert_eq!(iter1.as_slice(), iter2.as_slice());
+        }
+
+        let mut iter1 = fake_signature.into_iter();
+        let mut iter2 = fake_signature.iter();
+
+        // manual next_back instead of rev() so that we can check as_slice()
+        // if next_back is implemented correctly then rev() is also correct - provided by `core`
+        while let (Some(a), Some(b)) = (iter1.next_back(), iter2.next_back()) {
+            assert_eq!(a, *b);
+            assert_eq!(iter1.size_hint(), iter2.size_hint());
+            assert_eq!(iter1.as_slice(), iter2.as_slice());
+        }
+    }
+}
diff --git a/bitcoin/src/taproot/mod.rs b/bitcoin/src/taproot/mod.rs
index 24bf7fa6..b860cc43 100644
--- a/bitcoin/src/taproot/mod.rs
+++ b/bitcoin/src/taproot/mod.rs
@@ -5,7 +5,6 @@
 //! This module provides support for Taproot tagged hashes.
 
 pub mod merkle_branch;
-pub mod serialized_signature;
 
 use core::cmp::{Ordering, Reverse};
 use core::convert::Infallible;
@@ -32,7 +31,7 @@ use crate::{TapScript, TapScriptBuf};
 // Re-export these so downstream only has to use one `taproot` module.
 #[rustfmt::skip]
 #[doc(inline)]
-pub use crate::crypto::taproot::{SigFromSliceError, Signature};
+pub use crate::crypto::taproot::{SerializedSignature, SigFromSliceError, Signature};
 #[doc(inline)]
 pub use merkle_branch::TaprootMerkleBranch;
 #[doc(inline)]
diff --git a/bitcoin/src/taproot/serialized_signature.rs b/bitcoin/src/taproot/serialized_signature.rs
deleted file mode 100644
index 839fc5bf..00000000
--- a/bitcoin/src/taproot/serialized_signature.rs
+++ /dev/null
@@ -1,296 +0,0 @@
-//! Implements [`SerializedSignature`] and related types.
-//!
-//! Serialized Taproot signatures have the issue that they can have different lengths.
-//! We want to avoid using `Vec` since that would require allocations making the code slower and
-//! unable to run on platforms without an allocator. We implement a special type to encapsulate
-//! serialized signatures and since it's a bit more complicated it has its own module.
-
-use core::borrow::Borrow;
-use core::{fmt, ops};
-
-pub use into_iter::IntoIter;
-use io::Write;
-
-use super::{SigFromSliceError, Signature};
-
-pub(crate) const MAX_LEN: usize = 65; // 64 for sig, 1B sighash flag
-
-/// A serialized Taproot Signature
-#[derive(Copy, Clone)]
-pub struct SerializedSignature {
-    data: [u8; MAX_LEN],
-    len: usize,
-}
-
-impl fmt::Debug for SerializedSignature {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { fmt::Display::fmt(self, f) }
-}
-
-impl fmt::Display for SerializedSignature {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        hex::fmt_hex_exact!(f, MAX_LEN, self, hex::Case::Lower)
-    }
-}
-
-impl PartialEq for SerializedSignature {
-    #[inline]
-    fn eq(&self, other: &Self) -> bool { **self == **other }
-}
-
-impl PartialEq<[u8]> for SerializedSignature {
-    #[inline]
-    fn eq(&self, other: &[u8]) -> bool { **self == *other }
-}
-
-impl PartialEq<SerializedSignature> for [u8] {
-    #[inline]
-    fn eq(&self, other: &SerializedSignature) -> bool { *self == **other }
-}
-
-impl PartialOrd for SerializedSignature {
-    fn partial_cmp(&self, other: &Self) -> Option<core::cmp::Ordering> {
-        Some(self.cmp(other))
-    }
-}
-
-impl Ord for SerializedSignature {
-    fn cmp(&self, other: &Self) -> core::cmp::Ordering { (**self).cmp(&**other) }
-}
-
-impl PartialOrd<[u8]> for SerializedSignature {
-    fn partial_cmp(&self, other: &[u8]) -> Option<core::cmp::Ordering> {
-        (**self).partial_cmp(other)
-    }
-}
-
-impl PartialOrd<SerializedSignature> for [u8] {
-    fn partial_cmp(&self, other: &SerializedSignature) -> Option<core::cmp::Ordering> {
-        self.partial_cmp(&**other)
-    }
-}
-
-impl core::hash::Hash for SerializedSignature {
-    fn hash<H: core::hash::Hasher>(&self, state: &mut H) { (**self).hash(state) }
-}
-
-impl AsRef<[u8]> for SerializedSignature {
-    #[inline]
-    fn as_ref(&self) -> &[u8] { self }
-}
-
-impl Borrow<[u8]> for SerializedSignature {
-    #[inline]
-    fn borrow(&self) -> &[u8] { self }
-}
-
-impl ops::Deref for SerializedSignature {
-    type Target = [u8];
-
-    #[inline]
-    fn deref(&self) -> &[u8] { &self.data[..self.len] }
-}
-
-impl Eq for SerializedSignature {}
-
-impl IntoIterator for SerializedSignature {
-    type IntoIter = IntoIter;
-    type Item = u8;
-
-    #[inline]
-    fn into_iter(self) -> Self::IntoIter { IntoIter::new(self) }
-}
-
-impl<'a> IntoIterator for &'a SerializedSignature {
-    type IntoIter = core::slice::Iter<'a, u8>;
-    type Item = &'a u8;
-
-    #[inline]
-    fn into_iter(self) -> Self::IntoIter { self.iter() }
-}
-
-impl From<Signature> for SerializedSignature {
-    fn from(value: Signature) -> Self { Self::from_signature(value) }
-}
-
-impl<'a> From<&'a Signature> for SerializedSignature {
-    fn from(value: &'a Signature) -> Self { Self::from_signature(*value) }
-}
-
-impl TryFrom<SerializedSignature> for Signature {
-    type Error = SigFromSliceError;
-
-    fn try_from(value: SerializedSignature) -> Result<Self, Self::Error> { value.to_signature() }
-}
-
-impl<'a> TryFrom<&'a SerializedSignature> for Signature {
-    type Error = SigFromSliceError;
-
-    fn try_from(value: &'a SerializedSignature) -> Result<Self, Self::Error> {
-        value.to_signature()
-    }
-}
-
-impl SerializedSignature {
-    /// Constructs new `SerializedSignature` from data and length.
-    ///
-    /// # Panics
-    ///
-    /// If `len` > `MAX_LEN`
-    #[inline]
-    pub(crate) fn from_raw_parts(data: [u8; MAX_LEN], len: usize) -> Self {
-        assert!(len <= MAX_LEN, "attempt to set length to {} but the maximum is {}", len, MAX_LEN);
-        Self { data, len }
-    }
-
-    /// Get the len of the used data.
-    // `len` is never 0, so `is_empty` would always return `false`.
-    #[allow(clippy::len_without_is_empty)]
-    #[inline]
-    pub fn len(&self) -> usize { self.len }
-
-    /// Set the length of the object.
-    #[inline]
-    pub(crate) fn set_len_unchecked(&mut self, len: usize) { self.len = len; }
-
-    /// Convert the serialized signature into the Signature struct.
-    /// (This deserializes it)
-    #[inline]
-    pub fn to_signature(self) -> Result<Signature, SigFromSliceError> {
-        Signature::from_slice(&self)
-    }
-
-    /// Constructs a new SerializedSignature from a Signature.
-    /// (this serializes it)
-    #[inline]
-    pub fn from_signature(sig: Signature) -> Self { sig.serialize() }
-
-    /// Writes this serialized signature to a `writer`.
-    #[inline]
-    pub fn write_to<W: Write + ?Sized>(&self, writer: &mut W) -> Result<(), io::Error> {
-        writer.write_all(self)
-    }
-}
-
-/// Separate mod to prevent outside code from accidentally breaking invariants.
-mod into_iter {
-    use super::*;
-
-    /// Owned iterator over the bytes of [`SerializedSignature`]
-    ///
-    /// Created by [`IntoIterator::into_iter`] method.
-    // allowed because of https://github.com/rust-lang/rust/issues/98348
-    #[allow(missing_copy_implementations)]
-    #[derive(Debug, Clone)]
-    pub struct IntoIter {
-        signature: SerializedSignature,
-        // invariant: pos <= signature.len()
-        pos: usize,
-    }
-
-    impl IntoIter {
-        #[inline]
-        pub(crate) fn new(signature: SerializedSignature) -> Self {
-            Self {
-                signature,
-                // for all unsigned n: 0 <= n
-                pos: 0,
-            }
-        }
-
-        /// Returns the remaining bytes as a slice.
-        ///
-        /// This method is analogous to [`core::slice::Iter::as_slice`].
-        #[inline]
-        pub fn as_slice(&self) -> &[u8] { &self.signature[self.pos..] }
-    }
-
-    impl Iterator for IntoIter {
-        type Item = u8;
-
-        #[inline]
-        fn next(&mut self) -> Option<Self::Item> {
-            let byte = *self.signature.get(self.pos)?;
-            // can't overflow or break invariant because if pos is too large we return early
-            self.pos += 1;
-            Some(byte)
-        }
-
-        #[inline]
-        fn size_hint(&self) -> (usize, Option<usize>) {
-            // can't overflow thanks to the invariant
-            let len = self.signature.len() - self.pos;
-            (len, Some(len))
-        }
-
-        // override for speed
-        #[inline]
-        fn nth(&mut self, n: usize) -> Option<Self::Item> {
-            if n >= self.len() {
-                // upholds invariant because the values will be equal
-                self.pos = self.signature.len();
-                None
-            } else {
-                // if n < signature.len() - self.pos then n + self.pos < signature.len() which neither
-                // overflows nor breaks the invariant
-                self.pos += n;
-                self.next()
-            }
-        }
-    }
-
-    impl ExactSizeIterator for IntoIter {}
-
-    impl core::iter::FusedIterator for IntoIter {}
-
-    impl DoubleEndedIterator for IntoIter {
-        #[inline]
-        fn next_back(&mut self) -> Option<Self::Item> {
-            if self.pos == self.signature.len() {
-                return None;
-            }
-
-            // if len is 0 then pos is also 0 thanks to the invariant so we would return before we
-            // reach this
-            let new_len = self.signature.len() - 1;
-            let byte = self.signature[new_len];
-            self.signature.set_len_unchecked(new_len);
-            Some(byte)
-        }
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::{SerializedSignature, MAX_LEN};
-
-    #[test]
-    fn iterator_ops_are_homomorphic() {
-        let mut fake_signature_data = [0; MAX_LEN];
-        for (i, byte) in fake_signature_data.iter_mut().enumerate() {
-            *byte = i as u8;
-        }
-
-        let fake_signature = SerializedSignature { data: fake_signature_data, len: MAX_LEN };
-
-        let mut iter1 = fake_signature.into_iter();
-        let mut iter2 = fake_signature.iter();
-
-        // while let so we can compare size_hint and as_slice
-        while let (Some(a), Some(b)) = (iter1.next(), iter2.next()) {
-            assert_eq!(a, *b);
-            assert_eq!(iter1.size_hint(), iter2.size_hint());
-            assert_eq!(iter1.as_slice(), iter2.as_slice());
-        }
-
-        let mut iter1 = fake_signature.into_iter();
-        let mut iter2 = fake_signature.iter();
-
-        // manual next_back instead of rev() so that we can check as_slice()
-        // if next_back is implemented correctly then rev() is also correct - provided by `core`
-        while let (Some(a), Some(b)) = (iter1.next_back(), iter2.next_back()) {
-            assert_eq!(a, *b);
-            assert_eq!(iter1.size_hint(), iter2.size_hint());
-            assert_eq!(iter1.as_slice(), iter2.as_slice());
-        }
-    }
-}