diff --git a/aes/src/block/block128.rs b/aes/src/block/block128.rs
index 3a43fd2..c7a17bb 100644
--- a/aes/src/block/block128.rs
+++ b/aes/src/block/block128.rs
@@ -2,7 +2,7 @@ use crate::{
     block::{Block32, secret_block},
     sbox::SboxLookup,
 };
-use cipher_core::{parse_block_int, BlockError, InputBlock};
+use cipher_core::{BlockError, InputBlock, parse_block_int};
 use std::{
     ops::BitXor,
     slice::{from_raw_parts, from_raw_parts_mut},
diff --git a/aes/src/block/mod.rs b/aes/src/block/mod.rs
index ad47237..6e6f358 100644
--- a/aes/src/block/mod.rs
+++ b/aes/src/block/mod.rs
@@ -1,6 +1,5 @@
 mod block128;
 mod block32;
-mod secret_block;
 
-use crate::secret_block;
+use cipher_core::secret_block;
 pub use {block32::Block32, block128::Block128};
diff --git a/aes/src/block/secret_block.rs b/aes/src/block/secret_block.rs
deleted file mode 100644
index eb3432f..0000000
--- a/aes/src/block/secret_block.rs
+++ /dev/null
@@ -1,190 +0,0 @@
-/// Macro to generate a masked, zeroizable integer wrapper type.
-///
-/// Usage:
-/// ```
-/// use des::secret_block;
-/// secret_block! {
-///     /// docs...
-///     pub struct Block48(u64, 48, 0x0000_FFFF_FFFF_FFFFu64);
-/// }
-/// ```
-#[macro_export]
-macro_rules! secret_block {
-    (
-    $(#[$meta:meta])*
-    $vis:vis struct $name:ident ( $int:tt, $bits:expr, $mask:expr );
-) => {
-        $(#[$meta])*
-        #[derive(Debug, Clone, Copy, PartialEq, Eq)]
-        $vis struct $name($int);
-
-        impl $name {
-            /// Mask to restrict the underlying integer to valid bits.
-            pub const MASK: $int = $mask;
-
-            /// Calculate the number of hex digits needed for the bit width
-            const fn hex_width() -> usize {
-                ($bits as usize).div_ceil(4)
-            }
-
-            /// Calculate the number of octal digits needed for the bit width
-            const fn octal_width() -> usize {
-                ($bits as usize).div_ceil(3)
-            }
-
-            #[inline]
-            #[must_use]
-            pub const fn new(value: $int) -> Self {
-                Self(value & Self::MASK)
-            }
-
-            secret_block!(@conversions_as $int);
-            secret_block!(@conversions_from $int $int);
-        }
-
-        impl From<$int> for $name {
-            fn from(v: $int) -> Self {
-                Self(v & Self::MASK)
-            }
-        }
-
-        impl From<$name> for $int {
-            fn from(value: $name) -> $int {
-                value.0
-            }
-        }
-
-        impl std::fmt::UpperHex for $name {
-            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-                write!(f, "{:0width$X}", self.0, width = Self::hex_width())
-            }
-        }
-
-        impl std::fmt::LowerHex for $name {
-            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-                write!(f, "{:0width$x}", self.0, width = Self::hex_width())
-            }
-        }
-
-        impl std::fmt::Octal for $name {
-            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-                write!(f, "{:0width$o}", self.0, width = Self::octal_width())
-            }
-        }
-
-        impl std::fmt::Binary for $name {
-            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-                write!(f, "{:0width$b}", self.0, width = $bits)
-            }
-        }
-
-    };
-    // Helper: generate conversions_as based on type
-    (@conversions_as u8) => {
-        /// Return value as u8
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u8(&self) -> u8 {
-            self.0 as u8
-        }
-
-        secret_block!(@conversions_as u16);
-    };
-    (@conversions_as u16) => {
-        /// Return value as u16
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u16(&self) -> u16 {
-            self.0 as u16
-        }
-
-        secret_block!(@conversions_as u32);
-    };
-    (@conversions_as u32) => {
-        /// Return value as u32
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u32(&self) -> u32 {
-            self.0 as u32
-        }
-
-        secret_block!(@conversions_as u64);
-    };
-    (@conversions_as u64) => {
-        /// Return value as u64
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u64(&self) -> u64 {
-            self.0 as u64
-        }
-
-        secret_block!(@conversions_as u128);
-    };
-    (@conversions_as u128) => {
-        /// Return value as u129
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u128(&self) -> u128 {
-            self.0 as u128
-        }
-    };
-    // Helper: generate conversions_from based on type
-    (@conversions_from u8 $int:tt) => {
-        /// Create value from u8
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u8(key: u8) -> Self {
-            Self(key as $int & Self::MASK)
-        }
-    };
-    (@conversions_from u16 $int:tt) => {
-        /// Create value from u16
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u16(key: u16) -> Self {
-            Self(key as $int & Self::MASK)
-        }
-
-        secret_block!(@conversions_from u8 $int);
-    };
-    (@conversions_from u32 $int:tt) => {
-        /// Create value from u32
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u32(key: u32) -> Self {
-            Self(key as $int & Self::MASK)
-        }
-
-        secret_block!(@conversions_from u16 $int);
-    };
-    (@conversions_from u64 $int:tt) => {
-        /// Create value from u64
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u64(key: u64) -> Self {
-            Self(key as $int & Self::MASK)
-        }
-
-        secret_block!(@conversions_from u32 $int);
-    };
-    (@conversions_from u128 $int:tt) => {
-        /// Create value from u128
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u128(key: u128) -> Self {
-            Self(key & Self::MASK)
-        }
-
-        secret_block!(@conversions_from u64 $int);
-    }
-}
diff --git a/aes/src/key/expanded.rs b/aes/src/key/expanded.rs
deleted file mode 100644
index bc047b7..0000000
--- a/aes/src/key/expanded.rs
+++ /dev/null
@@ -1,5 +0,0 @@
-use crate::secret_key;
-
-secret_key! {
-    pub struct ExpandedKey(u32, 32, 0xFFFF_FFFF);
-}
diff --git a/aes/src/key/mod.rs b/aes/src/key/mod.rs
index 9bbdd55..a4ac36c 100644
--- a/aes/src/key/mod.rs
+++ b/aes/src/key/mod.rs
@@ -1,7 +1,6 @@
 mod aes_key;
-mod secret_key;
 mod subkey;
 mod subkeys;
 
-use crate::secret_key;
+use cipher_core::secret_key;
 pub use {aes_key::Key, subkey::Subkey, subkeys::Subkeys};
diff --git a/aes/src/key/secret_key.rs b/aes/src/key/secret_key.rs
deleted file mode 100644
index 1b6346f..0000000
--- a/aes/src/key/secret_key.rs
+++ /dev/null
@@ -1,149 +0,0 @@
-/// Macro to generate a masked, zeroizable integer wrapper type.
-///
-/// Usage:
-/// ```
-/// use des::secret_key;
-/// secret_key! {
-///     /// docs...
-///     pub struct Subkey(u64, 48, 0x0000_FFFF_FFFF_FFFFu64);
-/// }
-/// ```
-#[macro_export]
-macro_rules! secret_key {
-    (
-    $(#[$meta:meta])*
-    $vis:vis struct $name:ident ( $int:tt, $bits:expr, $mask:expr );
-) => {
-        $(#[$meta])*
-        #[derive(Default, Clone, Copy)]
-        $vis struct $name($int);
-
-        impl $name {
-            /// Mask to restrict the underlying integer to valid bits.
-            pub const MASK: $int = $mask;
-
-            secret_key!(@conversions_as $int);
-            secret_key!(@conversions_from $int $int);
-        }
-
-        impl ::std::fmt::Debug for $name {
-            fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
-                f.write_str(concat!(stringify!($name), "[REDACTED]"))
-            }
-        }
-
-        impl From<$int> for $name {
-            fn from(v: $int) -> Self {
-                Self(v & Self::MASK)
-            }
-        }
-    };
-    // Helper: generate conversions_as based on type
-    (@conversions_as u8) => {
-        /// Return value as u8
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u8(&self) -> u8 {
-            self.0 as u8
-        }
-
-        secret_key!(@conversions_as u16);
-    };
-    (@conversions_as u16) => {
-        /// Return value as u16
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u16(&self) -> u16 {
-            self.0 as u16
-        }
-
-        secret_key!(@conversions_as u32);
-    };
-    (@conversions_as u32) => {
-        /// Return value as u32
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u32(&self) -> u32 {
-            self.0 as u32
-        }
-
-        secret_key!(@conversions_as u64);
-    };
-    (@conversions_as u64) => {
-        /// Return value as u64
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u64(&self) -> u64 {
-            self.0 as u64
-        }
-
-        secret_key!(@conversions_as u128);
-    };
-    (@conversions_as u128) => {
-        /// Return value as u128
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u128(&self) -> u128 {
-            self.0 as u128
-        }
-    };
-    // Helper: generate conversions_from based on type
-    (@conversions_from u8 $int:tt) => {
-        /// Create value from u8
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u8(key: u8) -> Self {
-            Self(key as $int & Self::MASK)
-        }
-    };
-    (@conversions_from u16 $int:tt) => {
-        /// Create value from u16
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u16(key: u16) -> Self {
-            Self(key as $int & Self::MASK)
-        }
-
-        secret_key!(@conversions_from u8 $int);
-    };
-    (@conversions_from u32 $int:tt) => {
-        /// Create value from u32
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u32(key: u32) -> Self {
-            Self(key as $int & Self::MASK)
-        }
-
-        secret_key!(@conversions_from u16 $int);
-    };
-    (@conversions_from u64 $int:tt) => {
-        /// Create value from u64
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u64(key: u64) -> Self {
-            Self(key as $int & Self::MASK)
-        }
-
-        secret_key!(@conversions_from u32 $int);
-    };
-    (@conversions_from u128 $int:tt) => {
-        /// Create value from u128
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u128(key: u128) -> Self {
-            Self(key & Self::MASK)
-        }
-
-        secret_key!(@conversions_from u64 $int);
-    }
-}
diff --git a/cipher-core/Cargo.toml b/cipher-core/Cargo.toml
index 09ffddb..485f605 100644
--- a/cipher-core/Cargo.toml
+++ b/cipher-core/Cargo.toml
@@ -6,6 +6,7 @@ edition.workspace = true
 
 [dependencies]
 thiserror.workspace = true
+zeroize.workspace = true
 
 [lints]
 workspace = true
diff --git a/cipher-core/src/lib.rs b/cipher-core/src/lib.rs
index d04f1dc..960d9e8 100644
--- a/cipher-core/src/lib.rs
+++ b/cipher-core/src/lib.rs
@@ -1,11 +1,12 @@
 mod error;
+mod macros;
 mod parsing;
 mod traits;
 mod types;
 
 pub use {
     error::{BlockError, CipherError, CipherResult},
-    parsing::{parse_block_int, BlockInt},
+    parsing::{BlockInt, parse_block_int},
     traits::{BlockCipher, BlockParser, InputBlock},
     types::{CipherAction, Output},
 };
diff --git a/cipher-core/src/macros.rs b/cipher-core/src/macros.rs
new file mode 100644
index 0000000..5cc91b4
--- /dev/null
+++ b/cipher-core/src/macros.rs
@@ -0,0 +1,265 @@
+/// Macro to generate a masked integer wrapper type for cipher blocks.
+///
+/// Generates a type with formatting traits, conversions, and security features.
+///
+/// # Example
+/// ```ignore
+/// secret_block! {
+///     pub struct Block64(u64, 64, 0xFFFF_FFFF_FFFF_FFFF);
+/// }
+/// ```
+#[macro_export]
+macro_rules! secret_block {
+    (
+        $(#[$meta:meta])*
+        $vis:vis struct $name:ident ( $int:tt, $bits:expr, $mask:expr );
+    ) => {
+        $(#[$meta])*
+        #[derive(Debug, Clone, Copy, PartialEq, Eq, ::zeroize::Zeroize)]
+        $vis struct $name($int);
+
+        impl $name {
+            /// Mask to restrict the underlying integer to valid bits.
+            pub const MASK: $int = $mask;
+
+            const fn hex_width() -> usize {
+                ($bits as usize).div_ceil(4)
+            }
+
+            const fn octal_width() -> usize {
+                ($bits as usize).div_ceil(3)
+            }
+
+            #[inline]
+            #[must_use]
+            pub const fn new(value: $int) -> Self {
+                Self(value & Self::MASK)
+            }
+
+            $crate::secret_block!(@conversions_as $int);
+            $crate::secret_block!(@conversions_from $int $int);
+        }
+
+        impl From<$int> for $name {
+            fn from(v: $int) -> Self {
+                Self(v & Self::MASK)
+            }
+        }
+
+        impl From<$name> for $int {
+            fn from(value: $name) -> $int {
+                value.0
+            }
+        }
+
+        impl ::std::fmt::UpperHex for $name {
+            fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+                write!(f, "{:0width$X}", self.0, width = Self::hex_width())
+            }
+        }
+
+        impl ::std::fmt::LowerHex for $name {
+            fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+                write!(f, "{:0width$x}", self.0, width = Self::hex_width())
+            }
+        }
+
+        impl ::std::fmt::Octal for $name {
+            fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+                write!(f, "{:0width$o}", self.0, width = Self::octal_width())
+            }
+        }
+
+        impl ::std::fmt::Binary for $name {
+            fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+                write!(f, "{:0width$b}", self.0, width = $bits)
+            }
+        }
+    };
+
+    // Conversion chain: as_u8 -> as_u16 -> as_u32 -> as_u64 -> as_u128
+    (@conversions_as u8) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn as_u8(&self) -> u8 { self.0 as u8 }
+        $crate::secret_block!(@conversions_as u16);
+    };
+    (@conversions_as u16) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn as_u16(&self) -> u16 { self.0 as u16 }
+        $crate::secret_block!(@conversions_as u32);
+    };
+    (@conversions_as u32) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn as_u32(&self) -> u32 { self.0 as u32 }
+        $crate::secret_block!(@conversions_as u64);
+    };
+    (@conversions_as u64) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn as_u64(&self) -> u64 { self.0 as u64 }
+        $crate::secret_block!(@conversions_as u128);
+    };
+    (@conversions_as u128) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn as_u128(&self) -> u128 { self.0 as u128 }
+    };
+
+    // Conversion chain: from_u128 -> from_u64 -> from_u32 -> from_u16 -> from_u8
+    (@conversions_from u8 $int:tt) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn from_u8(v: u8) -> Self { Self(v as $int & Self::MASK) }
+    };
+    (@conversions_from u16 $int:tt) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn from_u16(v: u16) -> Self { Self(v as $int & Self::MASK) }
+        $crate::secret_block!(@conversions_from u8 $int);
+    };
+    (@conversions_from u32 $int:tt) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn from_u32(v: u32) -> Self { Self(v as $int & Self::MASK) }
+        $crate::secret_block!(@conversions_from u16 $int);
+    };
+    (@conversions_from u64 $int:tt) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn from_u64(v: u64) -> Self { Self(v as $int & Self::MASK) }
+        $crate::secret_block!(@conversions_from u32 $int);
+    };
+    (@conversions_from u128 $int:tt) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn from_u128(v: u128) -> Self { Self(v as $int & Self::MASK) }
+        $crate::secret_block!(@conversions_from u64 $int);
+    };
+}
+
+/// Macro to generate a masked integer wrapper type for cipher keys.
+///
+/// Keys have redacted Debug output and are zeroized on drop for security.
+///
+/// # Example
+/// ```ignore
+/// secret_key! {
+///     pub struct Key(u64, 64, 0xFFFF_FFFF_FFFF_FFFF);
+/// }
+/// ```
+#[macro_export]
+macro_rules! secret_key {
+    (
+        $(#[$meta:meta])*
+        $vis:vis struct $name:ident ( $int:tt, $bits:expr, $mask:expr );
+    ) => {
+        $(#[$meta])*
+        #[derive(Default, Clone, Copy, ::zeroize::Zeroize)]
+        $vis struct $name($int);
+
+        impl $name {
+            /// Mask to restrict the underlying integer to valid bits.
+            pub const MASK: $int = $mask;
+
+            $crate::secret_key!(@conversions_as $int);
+            $crate::secret_key!(@conversions_from $int $int);
+        }
+
+        impl ::std::fmt::Debug for $name {
+            fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+                f.write_str(concat!(stringify!($name), "[REDACTED]"))
+            }
+        }
+
+        impl From<$int> for $name {
+            fn from(v: $int) -> Self {
+                Self(v & Self::MASK)
+            }
+        }
+    };
+
+    // Conversion chain: as_u8 -> as_u16 -> as_u32 -> as_u64 -> as_u128
+    (@conversions_as u8) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn as_u8(&self) -> u8 { self.0 as u8 }
+        $crate::secret_key!(@conversions_as u16);
+    };
+    (@conversions_as u16) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn as_u16(&self) -> u16 { self.0 as u16 }
+        $crate::secret_key!(@conversions_as u32);
+    };
+    (@conversions_as u32) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn as_u32(&self) -> u32 { self.0 as u32 }
+        $crate::secret_key!(@conversions_as u64);
+    };
+    (@conversions_as u64) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn as_u64(&self) -> u64 { self.0 as u64 }
+        $crate::secret_key!(@conversions_as u128);
+    };
+    (@conversions_as u128) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn as_u128(&self) -> u128 { self.0 as u128 }
+    };
+
+    // Conversion chain: from_u128 -> from_u64 -> from_u32 -> from_u16 -> from_u8
+    (@conversions_from u8 $int:tt) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn from_u8(v: u8) -> Self { Self(v as $int & Self::MASK) }
+    };
+    (@conversions_from u16 $int:tt) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn from_u16(v: u16) -> Self { Self(v as $int & Self::MASK) }
+        $crate::secret_key!(@conversions_from u8 $int);
+    };
+    (@conversions_from u32 $int:tt) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn from_u32(v: u32) -> Self { Self(v as $int & Self::MASK) }
+        $crate::secret_key!(@conversions_from u16 $int);
+    };
+    (@conversions_from u64 $int:tt) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn from_u64(v: u64) -> Self { Self(v as $int & Self::MASK) }
+        $crate::secret_key!(@conversions_from u32 $int);
+    };
+    (@conversions_from u128 $int:tt) => {
+        #[allow(dead_code)]
+        #[inline]
+        #[must_use]
+        pub const fn from_u128(v: u128) -> Self { Self(v as $int & Self::MASK) }
+        $crate::secret_key!(@conversions_from u64 $int);
+    };
+}
diff --git a/des/src/block/block32.rs b/des/src/block/block32.rs
index 8e3501f..5a2e26d 100644
--- a/des/src/block/block32.rs
+++ b/des/src/block/block32.rs
@@ -1,6 +1,6 @@
 use std::ops::BitXor;
 
-use crate::secret_block;
+use super::secret_block;
 
 secret_block! {
     pub struct Block32(u32, 32, 0xFFFF_FFFF);
diff --git a/des/src/block/block48.rs b/des/src/block/block48.rs
index 576232b..dbac787 100644
--- a/des/src/block/block48.rs
+++ b/des/src/block/block48.rs
@@ -1,4 +1,5 @@
-use crate::{block::Block6, key::Subkey, secret_block};
+use super::{Block6, secret_block};
+use crate::key::Subkey;
 use std::{array, ops::BitXor};
 
 secret_block! {
diff --git a/des/src/block/block6.rs b/des/src/block/block6.rs
index 2c5fb0c..2d040bf 100644
--- a/des/src/block/block6.rs
+++ b/des/src/block/block6.rs
@@ -1,4 +1,4 @@
-use crate::secret_block;
+use super::secret_block;
 
 secret_block! {
     pub struct Block6(u8, 6, 0x3F);
diff --git a/des/src/block/block64.rs b/des/src/block/block64.rs
index 5bfedf8..06fe572 100644
--- a/des/src/block/block64.rs
+++ b/des/src/block/block64.rs
@@ -1,5 +1,5 @@
 use crate::block::{lr::LR, secret_block};
-use cipher_core::{parse_block_int, BlockError, InputBlock};
+use cipher_core::{BlockError, InputBlock, parse_block_int};
 use std::{
     slice::{from_raw_parts, from_raw_parts_mut},
     str::FromStr,
diff --git a/des/src/block/mod.rs b/des/src/block/mod.rs
index d4672b0..f674661 100644
--- a/des/src/block/mod.rs
+++ b/des/src/block/mod.rs
@@ -3,7 +3,6 @@ mod block48;
 mod block6;
 mod block64;
 mod lr;
-mod secret_block;
 
-use crate::secret_block;
+use cipher_core::secret_block;
 pub use {block6::Block6, block32::Block32, block48::Block48, block64::Block64, lr::LR};
diff --git a/des/src/block/secret_block.rs b/des/src/block/secret_block.rs
deleted file mode 100644
index 5032c8b..0000000
--- a/des/src/block/secret_block.rs
+++ /dev/null
@@ -1,168 +0,0 @@
-/// Macro to generate a masked, zeroizable integer wrapper type.
-///
-/// Usage:
-/// ```
-/// use des::secret_block;
-/// secret_block! {
-///     /// docs...
-///     pub struct Block48(u64, 48, 0x0000_FFFF_FFFF_FFFFu64);
-/// }
-/// ```
-#[macro_export]
-macro_rules! secret_block {
-    (
-    $(#[$meta:meta])*
-    $vis:vis struct $name:ident ( $int:tt, $bits:expr, $mask:expr );
-) => {
-        $(#[$meta])*
-        #[derive(Debug, Clone, Copy, PartialEq, Eq, ::zeroize::Zeroize)]
-        $vis struct $name($int);
-
-        impl $name {
-            /// Mask to restrict the underlying integer to valid bits.
-            pub const MASK: $int = $mask;
-
-            /// Calculate the number of hex digits needed for the bit width
-            const fn hex_width() -> usize {
-                ($bits as usize).div_ceil(4)
-            }
-
-            /// Calculate the number of octal digits needed for the bit width
-            const fn octal_width() -> usize {
-                ($bits as usize).div_ceil(3)
-            }
-
-            #[inline]
-            #[must_use]
-            pub const fn new(value: $int) -> Self {
-                Self(value & Self::MASK)
-            }
-
-            secret_block!(@conversions_as $int);
-            secret_block!(@conversions_from $int $int);
-        }
-
-        impl From<$int> for $name {
-            fn from(v: $int) -> Self {
-                Self(v & Self::MASK)
-            }
-        }
-
-        impl From<$name> for $int {
-            fn from(value: $name) -> $int {
-                value.0
-            }
-        }
-
-        impl std::fmt::UpperHex for $name {
-            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-                write!(f, "{:0width$X}", self.0, width = Self::hex_width())
-            }
-        }
-
-        impl std::fmt::LowerHex for $name {
-            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-                write!(f, "{:0width$x}", self.0, width = Self::hex_width())
-            }
-        }
-
-        impl std::fmt::Octal for $name {
-            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-                write!(f, "{:0width$o}", self.0, width = Self::octal_width())
-            }
-        }
-
-        impl std::fmt::Binary for $name {
-            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-                write!(f, "{:0width$b}", self.0, width = $bits)
-            }
-        }
-
-    };
-    // Helper: generate conversions_as based on type
-    (@conversions_as u8) => {
-        /// Return value as u8
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u8(&self) -> u8 {
-            self.0 as u8
-        }
-
-        secret_block!(@conversions_as u16);
-    };
-    (@conversions_as u16) => {
-        /// Return value as u16
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u16(&self) -> u16 {
-            self.0 as u16
-        }
-
-        secret_block!(@conversions_as u32);
-    };
-    (@conversions_as u32) => {
-        /// Return value as u32
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u32(&self) -> u32 {
-            self.0 as u32
-        }
-
-        secret_block!(@conversions_as u64);
-    };
-    (@conversions_as u64) => {
-        /// Return value as u64
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u64(&self) -> u64 {
-            self.0 as u64
-        }
-    };
-    // Helper: generate conversions_from based on type
-    (@conversions_from u8 $int:tt) => {
-        /// Create value from u8
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u8(key: u8) -> Self {
-            Self(key as $int & Self::MASK)
-        }
-    };
-    (@conversions_from u16 $int:tt) => {
-        /// Create value from u16
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u16(key: u16) -> Self {
-            Self(key as $int & Self::MASK)
-        }
-
-        secret_block!(@conversions_from u8 $int);
-    };
-    (@conversions_from u32 $int:tt) => {
-        /// Create value from u32
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u32(key: u32) -> Self {
-            Self(key as $int & Self::MASK)
-        }
-
-        secret_block!(@conversions_from u16 $int);
-    };
-    (@conversions_from u64 $int:tt) => {
-        /// Create value from u64
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u64(key: u64) -> Self {
-            Self(key & Self::MASK)
-        }
-
-        secret_block!(@conversions_from u32 $int);
-    }
-}
diff --git a/des/src/des.rs b/des/src/des.rs
index 777040d..93834bb 100644
--- a/des/src/des.rs
+++ b/des/src/des.rs
@@ -81,21 +81,21 @@ where
 {
     let mut lr = LR::from(block);
 
-    for subkey in subkeys {
+    for &subkey in subkeys {
         feistel(&mut lr, subkey);
     }
     lr.swap();
     lr.into()
 }
 
-fn feistel(lr: &mut LR, subkey: &Subkey) {
+fn feistel(lr: &mut LR, subkey: Subkey) {
     let tmp = lr.right;
     lr.right = lr.left ^ f_function(lr.right, subkey);
     lr.left = tmp;
 }
 
 #[must_use]
-fn f_function(right: Block32, subkey: &Subkey) -> Block32 {
+fn f_function(right: Block32, subkey: Subkey) -> Block32 {
     let expanded = expansion_permutation(right);
     let xored = expanded ^ subkey;
     let sboxed = s_box_substitution(xored);
diff --git a/des/src/key/cd56.rs b/des/src/key/cd56.rs
index 2f59851..9c90830 100644
--- a/des/src/key/cd56.rs
+++ b/des/src/key/cd56.rs
@@ -1,7 +1,7 @@
 use crate::key::{half28::Half28, key56::Key56};
 use zeroize::ZeroizeOnDrop;
 
-#[derive(ZeroizeOnDrop)]
+#[derive(Clone, ZeroizeOnDrop)]
 pub struct CD56 {
     pub c: Half28,
     pub d: Half28,
@@ -14,7 +14,7 @@ impl CD56 {
         Self { c, d }
     }
 
-    pub fn rotate_left(&mut self, amount: u8) {
+    pub const fn rotate_left(&mut self, amount: u8) {
         self.c = self.c.rotate_left(amount);
         self.d = self.d.rotate_left(amount);
     }
@@ -22,12 +22,12 @@ impl CD56 {
 
 impl From<CD56> for Key56 {
     fn from(value: CD56) -> Self {
-        Self::from_half28(&value.c, &value.d)
+        Self::from_half28(value.c, value.d)
     }
 }
 
 impl From<&CD56> for Key56 {
     fn from(value: &CD56) -> Self {
-        Self::from_half28(&value.c, &value.d)
+        Self::from_half28(value.c, value.d)
     }
 }
diff --git a/des/src/key/half28.rs b/des/src/key/half28.rs
index fa3ee76..9181a1b 100644
--- a/des/src/key/half28.rs
+++ b/des/src/key/half28.rs
@@ -7,7 +7,7 @@ secret_key! {
 
 impl Half28 {
     #[must_use]
-    pub const fn rotate_left(&self, amount: u8) -> Self {
+    pub const fn rotate_left(self, amount: u8) -> Self {
         let value = self.0;
         let main_shifted = (value << amount) & Self::MASK;
         let wrapped_bits = (value >> (28 - amount)) & ((1 << amount) - 1);
diff --git a/des/src/key/key56.rs b/des/src/key/key56.rs
index 356440a..81202ba 100644
--- a/des/src/key/key56.rs
+++ b/des/src/key/key56.rs
@@ -1,7 +1,4 @@
-use crate::{
-    key::{cd56::CD56, half28::Half28},
-    secret_key,
-};
+use super::{cd56::CD56, half28::Half28, secret_key};
 
 secret_key! {
     /// 56-bit key after PC-1 (lower 56 bits used).
@@ -10,14 +7,14 @@ secret_key! {
 
 impl Key56 {
     #[must_use]
-    pub const fn split(&self) -> CD56 {
+    pub const fn split(self) -> CD56 {
         let c = ((self.0 >> 28) & 0x0FFF_FFFF) as u32;
         let d = (self.0 & 0x0FFF_FFFF) as u32;
         CD56::new(Half28::from_u32(c), Half28::from_u32(d))
     }
 
     #[must_use]
-    pub const fn from_half28(left: &Half28, right: &Half28) -> Self {
+    pub const fn from_half28(left: Half28, right: Half28) -> Self {
         let left = left.as_u64();
         let right = right.as_u64();
         Self::from_u64((left << 28) | right)
diff --git a/des/src/key/mod.rs b/des/src/key/mod.rs
index 6db9f79..3947c3f 100644
--- a/des/src/key/mod.rs
+++ b/des/src/key/mod.rs
@@ -2,9 +2,8 @@ mod cd56;
 mod des_key;
 mod half28;
 mod key56;
-mod secret_key;
 mod subkey;
 mod subkeys;
 
-use crate::secret_key;
+use cipher_core::secret_key;
 pub use {des_key::Key, subkey::Subkey, subkeys::Subkeys};
diff --git a/des/src/key/secret_key.rs b/des/src/key/secret_key.rs
deleted file mode 100644
index a935415..0000000
--- a/des/src/key/secret_key.rs
+++ /dev/null
@@ -1,127 +0,0 @@
-/// Macro to generate a masked, zeroizable integer wrapper type.
-///
-/// Usage:
-/// ```
-/// use des::secret_key;
-/// secret_key! {
-///     /// docs...
-///     pub struct Subkey(u64, 48, 0x0000_FFFF_FFFF_FFFFu64);
-/// }
-/// ```
-#[macro_export]
-macro_rules! secret_key {
-    (
-    $(#[$meta:meta])*
-    $vis:vis struct $name:ident ( $int:tt, $bits:expr, $mask:expr );
-) => {
-        $(#[$meta])*
-        #[derive(::zeroize::ZeroizeOnDrop, Default)]
-        $vis struct $name($int);
-
-        impl $name {
-            /// Mask to restrict the underlying integer to valid bits.
-            pub const MASK: $int = $mask;
-
-            secret_key!(@conversions_as $int);
-            secret_key!(@conversions_from $int $int);
-        }
-
-        impl ::std::fmt::Debug for $name {
-            fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
-                f.write_str(concat!(stringify!($name), "[REDACTED]"))
-            }
-        }
-
-        impl From<$int> for $name {
-            fn from(v: $int) -> Self {
-                Self(v & Self::MASK)
-            }
-        }
-    };
-    // Helper: generate conversions_as based on type
-    (@conversions_as u8) => {
-        /// Return value as u8
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u8(&self) -> u8 {
-            self.0 as u8
-        }
-
-        secret_key!(@conversions_as u16);
-    };
-    (@conversions_as u16) => {
-        /// Return value as u16
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u16(&self) -> u16 {
-            self.0 as u16
-        }
-
-        secret_key!(@conversions_as u32);
-    };
-    (@conversions_as u32) => {
-        /// Return value as u32
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u32(&self) -> u32 {
-            self.0 as u32
-        }
-
-        secret_key!(@conversions_as u64);
-    };
-    (@conversions_as u64) => {
-        /// Return value as u64
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn as_u64(&self) -> u64 {
-            self.0 as u64
-        }
-    };
-    // Helper: generate conversions_from based on type
-    (@conversions_from u8 $int:tt) => {
-        /// Create value from u8
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u8(key: u8) -> Self {
-            Self(key as $int & Self::MASK)
-        }
-    };
-    (@conversions_from u16 $int:tt) => {
-        /// Create value from u16
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u16(key: u16) -> Self {
-            Self(key as $int & Self::MASK)
-        }
-
-        secret_key!(@conversions_from u8 $int);
-    };
-    (@conversions_from u32 $int:tt) => {
-        /// Create value from u32
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u32(key: u32) -> Self {
-            Self(key as $int & Self::MASK)
-        }
-
-        secret_key!(@conversions_from u16 $int);
-    };
-    (@conversions_from u64 $int:tt) => {
-        /// Create value from u64
-        #[allow(dead_code)]
-        #[inline]
-        #[must_use]
-        pub const fn from_u64(key: u64) -> Self {
-            Self(key & Self::MASK)
-        }
-
-        secret_key!(@conversions_from u32 $int);
-    }
-}