diff --git a/Cargo.lock b/Cargo.lock
index 71ba591..f6d7cd4 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -40,9 +40,9 @@ checksum = "89af0b093cc13baa4e51e64e65ec2422f7e73aea0e612e5ad3872986671622f1"
 
 [[package]]
 name = "block-buffer"
-version = "0.11.0"
+version = "0.12.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "96eb4cdd6cf1b31d671e9efe75c5d1ec614776856cefbe109ca373554a6d514f"
+checksum = "cdd35008169921d80bc60d3d0ab416eecb028c4cd653352907921d95084790be"
 dependencies = [
  "hybrid-array",
  "zeroize",
@@ -67,9 +67,9 @@ checksum = "9330f8b2ff13f34540b44e946ef35111825727b38d33286ef986142615121801"
 
 [[package]]
 name = "cipher"
-version = "0.5.0"
+version = "0.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "64727038c8c5e2bb503a15b9f5b9df50a1da9a33e83e1f93067d914f2c6604a5"
+checksum = "e34d8227fe1ba289043aeb13792056ff80fd6de1a9f49137a5f499de8e8c78ea"
 dependencies = [
  "block-buffer",
  "crypto-common",
@@ -114,9 +114,9 @@ dependencies = [
 
 [[package]]
 name = "crypto-common"
-version = "0.2.0"
+version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "211f05e03c7d03754740fd9e585de910a095d6b99f8bcfffdef8319fa02a8331"
+checksum = "77727bb15fa921304124b128af125e7e3b968275d1b108b379190264f4423710"
 dependencies = [
  "hybrid-array",
 ]
@@ -150,9 +150,9 @@ dependencies = [
 
 [[package]]
 name = "digest"
-version = "0.11.0"
+version = "0.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f8bf3682cdec91817be507e4aa104314898b95b84d74f3d43882210101a545b6"
+checksum = "285743a676ccb6b3e116bc14cc69319b957867930ae9c4822f8e0f54509d7243"
 dependencies = [
  "blobby",
  "block-buffer",
@@ -210,9 +210,9 @@ dependencies = [
 
 [[package]]
 name = "libc"
-version = "0.2.180"
+version = "0.2.182"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bcc35a38544a891a5f7c865aca548a982ccb3b8650a5b06d0fd33a10283c56fc"
+checksum = "6800badb6cb2082ffd7b6a67e6125bb39f18782f793520caee8cb8846be06112"
 
 [[package]]
 name = "magma"
diff --git a/belt-mac/src/block_api.rs b/belt-mac/src/block_api.rs
index 3974f11..f090593 100644
--- a/belt-mac/src/block_api.rs
+++ b/belt-mac/src/block_api.rs
@@ -6,9 +6,10 @@ use digest::{
     array::{Array, ArraySize},
     block_api::{
         AlgorithmName, Block, BlockSizeUser, Buffer, BufferKindUser, FixedOutputCore, Lazy,
-        UpdateCore,
+        SmallBlockSizeUser, UpdateCore,
     },
-    common::{BlockSizes, InnerInit, InnerUser},
+    block_buffer::BlockSizes,
+    common::{InnerInit, InnerUser},
 };
 
 #[cfg(feature = "zeroize")]
@@ -18,7 +19,7 @@ use digest::zeroize::{Zeroize, ZeroizeOnDrop};
 #[derive(Clone)]
 pub struct BeltMacCore<C = BeltBlock>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     cipher: C,
     state: Block<C>,
@@ -27,30 +28,30 @@ where
 
 impl<C> BlockSizeUser for BeltMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     type BlockSize = C::BlockSize;
 }
 
 impl<C> OutputSizeUser for BeltMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     type OutputSize = C::BlockSize;
 }
 
 impl<C> InnerUser for BeltMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     type Inner = C;
 }
 
-impl<C> MacMarker for BeltMacCore<C> where C: BlockCipherEncrypt + Clone {}
+impl<C> MacMarker for BeltMacCore<C> where C: BlockCipherEncrypt + SmallBlockSizeUser + Clone {}
 
 impl<C> InnerInit for BeltMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     #[inline]
     fn inner_init(cipher: C) -> Self {
@@ -63,14 +64,14 @@ where
 
 impl<C> BufferKindUser for BeltMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     type BufferKind = Lazy;
 }
 
 impl<C> UpdateCore for BeltMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     #[inline]
     fn update_blocks(&mut self, blocks: &[Block<Self>]) {
@@ -100,7 +101,7 @@ where
 
 impl<C> Reset for BeltMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     #[inline(always)]
     fn reset(&mut self) {
@@ -110,7 +111,7 @@ where
 
 impl<C> FixedOutputCore for BeltMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     #[inline]
     fn finalize_fixed_core(&mut self, buffer: &mut Buffer<Self>, out: &mut Output<Self>) {
@@ -147,7 +148,7 @@ where
 
 impl<C> AlgorithmName for BeltMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     fn write_alg_name(f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.write_str("BeltMac")
@@ -156,7 +157,7 @@ where
 
 impl<C> fmt::Debug for BeltMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.write_str("BeltMacCore { ... }")
@@ -166,7 +167,7 @@ where
 #[cfg(feature = "zeroize")]
 impl<C> Drop for BeltMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     fn drop(&mut self) {
         self.state.zeroize();
@@ -174,7 +175,10 @@ where
 }
 
 #[cfg(feature = "zeroize")]
-impl<C> ZeroizeOnDrop for BeltMacCore<C> where C: BlockCipherEncrypt + Clone + ZeroizeOnDrop {}
+impl<C> ZeroizeOnDrop for BeltMacCore<C> where
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone + ZeroizeOnDrop
+{
+}
 
 #[inline(always)]
 fn xor<N: ArraySize>(buf: &mut Array<u8, N>, data: &Array<u8, N>) {
diff --git a/belt-mac/src/lib.rs b/belt-mac/src/lib.rs
index 53bec4e..0077725 100644
--- a/belt-mac/src/lib.rs
+++ b/belt-mac/src/lib.rs
@@ -14,10 +14,11 @@ pub use digest::{self, KeyInit, Mac};
 pub mod block_api;
 
 use cipher::BlockCipherEncrypt;
+use digest::block_api::SmallBlockSizeUser;
 
 digest::buffer_fixed!(
     /// BeltMac instance generic over block cipher.
-    pub struct GenericBeltMac<C: BlockCipherEncrypt + Clone>(block_api::BeltMacCore<C>);
+    pub struct GenericBeltMac<C: BlockCipherEncrypt + SmallBlockSizeUser + Clone>(block_api::BeltMacCore<C>);
     impl: ResetMacTraits AlgorithmName InnerInit;
 );
 
diff --git a/cbc-mac/src/block_api.rs b/cbc-mac/src/block_api.rs
index ffbdca7..e16a11d 100644
--- a/cbc-mac/src/block_api.rs
+++ b/cbc-mac/src/block_api.rs
@@ -5,9 +5,10 @@ use digest::{
     array::{Array, ArraySize},
     block_api::{
         AlgorithmName, Block, BlockSizeUser, Buffer, BufferKindUser, Eager, FixedOutputCore,
-        UpdateCore,
+        SmallBlockSizeUser, UpdateCore,
     },
-    common::{BlockSizes, InnerInit, InnerUser},
+    block_buffer::BlockSizes,
+    common::{InnerInit, InnerUser},
 };
 
 #[cfg(feature = "zeroize")]
@@ -17,7 +18,7 @@ use digest::zeroize::{Zeroize, ZeroizeOnDrop};
 #[derive(Clone)]
 pub struct CbcMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     cipher: C,
     state: Block<C>,
@@ -25,30 +26,30 @@ where
 
 impl<C> BlockSizeUser for CbcMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     type BlockSize = C::BlockSize;
 }
 
 impl<C> OutputSizeUser for CbcMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     type OutputSize = C::BlockSize;
 }
 
 impl<C> InnerUser for CbcMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     type Inner = C;
 }
 
-impl<C> MacMarker for CbcMacCore<C> where C: BlockCipherEncrypt + Clone {}
+impl<C> MacMarker for CbcMacCore<C> where C: BlockCipherEncrypt + SmallBlockSizeUser + Clone {}
 
 impl<C> InnerInit for CbcMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     #[inline]
     fn inner_init(cipher: C) -> Self {
@@ -59,14 +60,14 @@ where
 
 impl<C> BufferKindUser for CbcMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     type BufferKind = Eager;
 }
 
 impl<C> UpdateCore for CbcMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     #[inline]
     fn update_blocks(&mut self, blocks: &[Block<Self>]) {
@@ -96,7 +97,7 @@ where
 
 impl<C> Reset for CbcMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     #[inline(always)]
     fn reset(&mut self) {
@@ -106,7 +107,7 @@ where
 
 impl<C> FixedOutputCore for CbcMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     #[inline]
     fn finalize_fixed_core(&mut self, buffer: &mut Buffer<Self>, out: &mut Output<Self>) {
@@ -122,7 +123,7 @@ where
 
 impl<C> AlgorithmName for CbcMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone + AlgorithmName,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone + AlgorithmName,
 {
     fn write_alg_name(f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.write_str("CbcMac<")?;
@@ -133,7 +134,7 @@ where
 
 impl<C> fmt::Debug for CbcMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone + AlgorithmName,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone + AlgorithmName,
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.write_str("CbcMacCore<")?;
@@ -145,7 +146,7 @@ where
 #[cfg(feature = "zeroize")]
 impl<C> Drop for CbcMacCore<C>
 where
-    C: BlockCipherEncrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone,
 {
     fn drop(&mut self) {
         self.state.zeroize();
@@ -153,7 +154,10 @@ where
 }
 
 #[cfg(feature = "zeroize")]
-impl<C> ZeroizeOnDrop for CbcMacCore<C> where C: BlockCipherEncrypt + Clone + ZeroizeOnDrop {}
+impl<C> ZeroizeOnDrop for CbcMacCore<C> where
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone + ZeroizeOnDrop
+{
+}
 
 #[inline(always)]
 fn xor<N: ArraySize>(buf: &mut Array<u8, N>, data: &Array<u8, N>) {
diff --git a/cbc-mac/src/lib.rs b/cbc-mac/src/lib.rs
index 16f7e07..3607d6d 100644
--- a/cbc-mac/src/lib.rs
+++ b/cbc-mac/src/lib.rs
@@ -8,7 +8,7 @@
 #![forbid(unsafe_code)]
 #![warn(missing_docs)]
 
-pub use digest::{self, KeyInit, Mac};
+pub use digest::{self, KeyInit, Mac, block_api::SmallBlockSizeUser};
 
 mod block_api;
 
@@ -18,13 +18,13 @@ use digest::block_api::CoreProxy;
 
 digest::buffer_fixed!(
     /// Generic CBC-MAC instance.
-    pub struct CbcMac<C: BlockCipherEncrypt + Clone>(block_api::CbcMacCore<C>);
+    pub struct CbcMac<C: BlockCipherEncrypt + SmallBlockSizeUser + Clone>(block_api::CbcMacCore<C>);
     impl: ResetMacTraits InnerInit;
 );
 
 impl<C> AlgorithmName for CbcMac<C>
 where
-    C: BlockCipherEncrypt + Clone + AlgorithmName,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + Clone + AlgorithmName,
 {
     fn write_alg_name(f: &mut fmt::Formatter<'_>) -> fmt::Result {
         <Self as CoreProxy>::Core::write_alg_name(f)
diff --git a/cmac/src/block_api.rs b/cmac/src/block_api.rs
index 6719766..bb54652 100644
--- a/cmac/src/block_api.rs
+++ b/cmac/src/block_api.rs
@@ -6,9 +6,10 @@ use digest::{
     array::{Array, ArraySize},
     block_api::{
         AlgorithmName, Block, BlockSizeUser, Buffer, BufferKindUser, FixedOutputCore, Lazy,
-        UpdateCore,
+        SmallBlockSizeUser, UpdateCore,
     },
-    common::{BlockSizes, InnerInit, InnerUser},
+    block_buffer::BlockSizes,
+    common::{InnerInit, InnerUser},
 };
 
 #[cfg(feature = "zeroize")]
@@ -139,14 +140,14 @@ fn xor<N: ArraySize>(buf: &mut Array<u8, N>, data: &Array<u8, N>) {
 }
 
 /// Helper trait implemented for cipher supported by CMAC
-pub trait CmacCipher: BlockSizeUser + BlockCipherEncrypt + Clone {
+pub trait CmacCipher: SmallBlockSizeUser + BlockCipherEncrypt + Clone {
     /// Double block. See the [`Dbl`] trait docs for more information.
     fn dbl(block: Block<Self>) -> Block<Self>;
 }
 
 impl<C> CmacCipher for C
 where
-    Self: BlockSizeUser + BlockCipherEncrypt + Clone,
+    Self: SmallBlockSizeUser + BlockCipherEncrypt + Clone,
     Block<Self>: Dbl,
 {
     fn dbl(block: Block<Self>) -> Block<Self> {
diff --git a/pmac/src/block_api.rs b/pmac/src/block_api.rs
index 0f46fc0..0978492 100644
--- a/pmac/src/block_api.rs
+++ b/pmac/src/block_api.rs
@@ -6,7 +6,7 @@ use digest::{
     array::{Array, ArraySize},
     block_api::{
         AlgorithmName, Block, BlockSizeUser, Buffer, BufferKindUser, FixedOutputCore, Lazy,
-        UpdateCore,
+        SmallBlockSizeUser, UpdateCore,
     },
     common::{InnerInit, InnerUser},
     typenum::Unsigned,
@@ -217,7 +217,7 @@ fn xor<N: ArraySize>(buf: &mut Array<u8, N>, data: &Array<u8, N>) {
 ///
 /// Currently this trait is implemented for all block cipher encryptors
 /// with block size equal to 64 and 128 bits.
-pub trait PmacCipher: BlockSizeUser + BlockCipherEncrypt + Clone {
+pub trait PmacCipher: SmallBlockSizeUser + BlockCipherEncrypt + Clone {
     /// Double block. See the [`Dbl`] trait docs for more information.
     fn dbl(block: Block<Self>) -> Block<Self>;
     /// Reverse double block.. See the [`Dbl`] trait docs for more information.
@@ -226,7 +226,7 @@ pub trait PmacCipher: BlockSizeUser + BlockCipherEncrypt + Clone {
 
 impl<C> PmacCipher for C
 where
-    Self: BlockSizeUser + BlockCipherEncrypt + Clone,
+    Self: SmallBlockSizeUser + BlockCipherEncrypt + Clone,
     Block<Self>: Dbl,
 {
     fn dbl(block: Block<Self>) -> Block<Self> {
diff --git a/retail-mac/src/block_api.rs b/retail-mac/src/block_api.rs
index 1320387..9a8f4ca 100644
--- a/retail-mac/src/block_api.rs
+++ b/retail-mac/src/block_api.rs
@@ -8,9 +8,9 @@ use digest::{
     array::{Array, ArraySize},
     block_api::{
         AlgorithmName, Block, BlockSizeUser, Buffer, BufferKindUser, Eager, FixedOutputCore,
-        UpdateCore,
+        SmallBlockSizeUser, UpdateCore,
     },
-    common::BlockSizes,
+    block_buffer::BlockSizes,
     typenum::{Prod, U2},
 };
 
@@ -21,7 +21,7 @@ use cipher::zeroize::{Zeroize, ZeroizeOnDrop};
 #[derive(Clone)]
 pub struct RetailMacCore<C>
 where
-    C: BlockCipherEncrypt + BlockCipherDecrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + BlockCipherDecrypt + Clone,
 {
     cipher: C,
     cipher_prime: C,
@@ -30,41 +30,44 @@ where
 
 impl<C> BlockSizeUser for RetailMacCore<C>
 where
-    C: BlockCipherEncrypt + BlockCipherDecrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + BlockCipherDecrypt + Clone,
 {
     type BlockSize = C::BlockSize;
 }
 
 impl<C> OutputSizeUser for RetailMacCore<C>
 where
-    C: BlockCipherEncrypt + BlockCipherDecrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + BlockCipherDecrypt + Clone,
 {
     type OutputSize = C::BlockSize;
 }
 
 impl<C> KeySizeUser for RetailMacCore<C>
 where
-    C: BlockCipherEncrypt + BlockCipherDecrypt + Clone,
-    <C as BlockSizeUser>::BlockSize: Mul<U2>,
-    Prod<<C as BlockSizeUser>::BlockSize, U2>: ArraySize,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + BlockCipherDecrypt + Clone,
+    <C as SmallBlockSizeUser>::_BlockSize: Mul<U2>,
+    Prod<<C as SmallBlockSizeUser>::_BlockSize, U2>: ArraySize,
 {
-    type KeySize = Prod<<C as BlockSizeUser>::BlockSize, U2>;
+    type KeySize = Prod<<C as SmallBlockSizeUser>::_BlockSize, U2>;
 }
 
-impl<C> MacMarker for RetailMacCore<C> where C: BlockCipherEncrypt + BlockCipherDecrypt + Clone {}
+impl<C> MacMarker for RetailMacCore<C> where
+    C: BlockCipherEncrypt + SmallBlockSizeUser + BlockCipherDecrypt + Clone
+{
+}
 
 impl<C> BufferKindUser for RetailMacCore<C>
 where
-    C: BlockCipherEncrypt + BlockCipherDecrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + BlockCipherDecrypt + Clone,
 {
     type BufferKind = Eager;
 }
 
 impl<C> KeyInit for RetailMacCore<C>
 where
-    C: BlockCipherEncrypt + BlockCipherDecrypt + Clone + KeyInit,
-    <C as BlockSizeUser>::BlockSize: Mul<U2>,
-    Prod<<C as BlockSizeUser>::BlockSize, U2>: ArraySize,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + BlockCipherDecrypt + Clone + KeyInit,
+    <C as SmallBlockSizeUser>::_BlockSize: Mul<U2>,
+    Prod<<C as SmallBlockSizeUser>::_BlockSize, U2>: ArraySize,
 {
     #[inline(always)]
     fn new(key: &Key<Self>) -> Self {
@@ -85,7 +88,7 @@ where
 
 impl<C> UpdateCore for RetailMacCore<C>
 where
-    C: BlockCipherEncrypt + BlockCipherDecrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + BlockCipherDecrypt + Clone,
 {
     #[inline]
     fn update_blocks(&mut self, blocks: &[Block<Self>]) {
@@ -115,7 +118,7 @@ where
 
 impl<C> Reset for RetailMacCore<C>
 where
-    C: BlockCipherEncrypt + BlockCipherDecrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + BlockCipherDecrypt + Clone,
 {
     #[inline(always)]
     fn reset(&mut self) {
@@ -125,7 +128,7 @@ where
 
 impl<C> FixedOutputCore for RetailMacCore<C>
 where
-    C: BlockCipherEncrypt + BlockCipherDecrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + BlockCipherDecrypt + Clone,
 {
     #[inline]
     fn finalize_fixed_core(&mut self, buffer: &mut Buffer<Self>, out: &mut Output<Self>) {
@@ -147,7 +150,7 @@ where
 
 impl<C> AlgorithmName for RetailMacCore<C>
 where
-    C: BlockCipherEncrypt + BlockCipherDecrypt + Clone + AlgorithmName,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + BlockCipherDecrypt + Clone + AlgorithmName,
 {
     fn write_alg_name(f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.write_str("RetailMac<")?;
@@ -158,7 +161,7 @@ where
 
 impl<C> fmt::Debug for RetailMacCore<C>
 where
-    C: BlockCipherEncrypt + BlockCipherDecrypt + Clone + AlgorithmName,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + BlockCipherDecrypt + Clone + AlgorithmName,
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.write_str("RetailMacCore<")?;
@@ -170,7 +173,7 @@ where
 #[cfg(feature = "zeroize")]
 impl<C> Drop for RetailMacCore<C>
 where
-    C: BlockCipherEncrypt + BlockCipherDecrypt + Clone,
+    C: BlockCipherEncrypt + SmallBlockSizeUser + BlockCipherDecrypt + Clone,
 {
     fn drop(&mut self) {
         self.state.zeroize();
@@ -179,7 +182,7 @@ where
 
 #[cfg(feature = "zeroize")]
 impl<C> ZeroizeOnDrop for RetailMacCore<C> where
-    C: BlockCipherEncrypt + BlockCipherDecrypt + Clone + ZeroizeOnDrop
+    C: BlockCipherEncrypt + SmallBlockSizeUser + BlockCipherDecrypt + Clone + ZeroizeOnDrop
 {
 }
 
diff --git a/retail-mac/src/lib.rs b/retail-mac/src/lib.rs
index 5d3eca8..a445bfb 100644
--- a/retail-mac/src/lib.rs
+++ b/retail-mac/src/lib.rs
@@ -14,35 +14,36 @@ pub use digest::{self, Key, KeyInit, Mac};
 pub mod block_api;
 
 use block_api::RetailMacCore;
-use cipher::{AlgorithmName, BlockCipherDecrypt, BlockCipherEncrypt, BlockSizeUser, KeySizeUser};
+use cipher::{AlgorithmName, BlockCipherDecrypt, BlockCipherEncrypt, KeySizeUser};
 use core::{fmt, ops::Mul};
 use digest::{
     InvalidLength,
     array::ArraySize,
     block_api::CoreProxy,
+    block_api::SmallBlockSizeUser,
     typenum::{Prod, U2},
 };
 
 digest::buffer_fixed!(
     /// Generic Retail MAC instance.
-    pub struct RetailMac<C: BlockCipherEncrypt + BlockCipherDecrypt + Clone>(RetailMacCore<C>);
+    pub struct RetailMac<C: BlockCipherEncrypt + BlockCipherDecrypt + SmallBlockSizeUser + Clone>(RetailMacCore<C>);
     impl: ResetMacTraits;
 );
 
 impl<C> KeySizeUser for RetailMac<C>
 where
-    C: BlockCipherEncrypt + BlockCipherDecrypt + Clone,
-    <C as BlockSizeUser>::BlockSize: Mul<U2>,
-    Prod<<C as BlockSizeUser>::BlockSize, U2>: ArraySize,
+    C: BlockCipherEncrypt + BlockCipherDecrypt + SmallBlockSizeUser + Clone,
+    <C as SmallBlockSizeUser>::_BlockSize: Mul<U2>,
+    Prod<<C as SmallBlockSizeUser>::_BlockSize, U2>: ArraySize,
 {
-    type KeySize = Prod<<C as BlockSizeUser>::BlockSize, U2>;
+    type KeySize = Prod<<C as SmallBlockSizeUser>::_BlockSize, U2>;
 }
 
 impl<C> KeyInit for RetailMac<C>
 where
-    C: BlockCipherEncrypt + BlockCipherDecrypt + Clone + KeyInit,
-    <C as BlockSizeUser>::BlockSize: Mul<U2>,
-    Prod<<C as BlockSizeUser>::BlockSize, U2>: ArraySize,
+    C: BlockCipherEncrypt + BlockCipherDecrypt + SmallBlockSizeUser + Clone + KeyInit,
+    <C as SmallBlockSizeUser>::_BlockSize: Mul<U2>,
+    Prod<<C as SmallBlockSizeUser>::_BlockSize, U2>: ArraySize,
 {
     #[inline(always)]
     fn new(key: &Key<Self>) -> Self {
@@ -63,7 +64,7 @@ where
 
 impl<C> AlgorithmName for RetailMac<C>
 where
-    C: BlockCipherEncrypt + BlockCipherDecrypt + Clone + AlgorithmName,
+    C: BlockCipherEncrypt + BlockCipherDecrypt + SmallBlockSizeUser + Clone + AlgorithmName,
 {
     fn write_alg_name(f: &mut fmt::Formatter<'_>) -> fmt::Result {
         <Self as CoreProxy>::Core::write_alg_name(f)