diff --git a/Crypto/Internal/ByteArray.hs b/Crypto/Internal/ByteArray.hs
index d7b1fbc..612833c 100644
--- a/Crypto/Internal/ByteArray.hs
+++ b/Crypto/Internal/ByteArray.hs
@@ -13,8 +13,11 @@
 module Crypto.Internal.ByteArray
     ( ByteArray(..)
     , ByteArrayAccess(..)
+    , byteArrayAlloc
     , byteArrayAllocAndFreeze
     , empty
+    , byteArrayCopy
+    , byteArrayCopyRet
     , byteArrayCopyAndFreeze
     , byteArraySplit
     , byteArrayXor
@@ -50,32 +53,35 @@ class ByteArrayAccess ba where
     withByteArray   :: ba -> (Ptr p -> IO a) -> IO a
 
 class ByteArrayAccess ba => ByteArray ba where
-    byteArrayAlloc  :: Int -> (Ptr p -> IO ()) -> IO ba
+    byteArrayAllocRet  :: Int -> (Ptr p -> IO a) -> IO (a, ba)
+
+byteArrayAlloc :: ByteArray ba => Int -> (Ptr p -> IO ()) -> IO ba
+byteArrayAlloc n f = snd `fmap` byteArrayAllocRet n f
 
 instance ByteArrayAccess Bytes where
     byteArrayLength = bytesLength
     withByteArray   = withBytes
 instance ByteArray Bytes where
-    byteArrayAlloc  = bytesAlloc
+    byteArrayAllocRet = bytesAllocRet
 
 instance ByteArrayAccess ByteString where
     byteArrayLength = B.length
     withByteArray b f = withForeignPtr fptr $ \ptr -> f (ptr `plusPtr` off)
       where (fptr, off, _) = B.toForeignPtr b
 instance ByteArray ByteString where
-    byteArrayAlloc sz f = do
+    byteArrayAllocRet sz f = do
         fptr <- B.mallocByteString sz
-        withForeignPtr fptr (f . castPtr)
-        return $! B.PS fptr 0 sz
+        r    <- withForeignPtr fptr (f . castPtr)
+        return (r, B.PS fptr 0 sz)
 
 instance ByteArrayAccess SecureMem where
     byteArrayLength = secureMemGetSize
     withByteArray b f = withSecureMemPtr b (f . castPtr)
 instance ByteArray SecureMem where
-    byteArrayAlloc sz f = do
+    byteArrayAllocRet sz f = do
         out <- allocateSecureMem sz
-        withSecureMemPtr out (f . castPtr)
-        return out
+        r   <- withSecureMemPtr out (f . castPtr)
+        return (r, out)
 
 byteArrayAllocAndFreeze :: ByteArray a => Int -> (Ptr p -> IO ()) -> a
 byteArrayAllocAndFreeze sz f = unsafeDoIO (byteArrayAlloc sz f)
@@ -123,6 +129,18 @@ byteArrayConcat allBs = byteArrayAllocAndFreeze total (loop allBs)
             withByteArray b $ \p -> bufCopy dst p sz
             loop bs (dst `plusPtr` sz)
 
+byteArrayCopy :: (ByteArray bs1, ByteArray bs2) => bs1 -> (Ptr p -> IO ()) -> IO bs2
+byteArrayCopy bs f =
+    byteArrayAlloc (byteArrayLength bs) $ \d -> do
+        withByteArray bs $ \s -> bufCopy d s (byteArrayLength bs)
+        f (castPtr d)
+
+byteArrayCopyRet :: (ByteArray bs1, ByteArray bs2) => bs1 -> (Ptr p -> IO a) -> IO (a, bs2)
+byteArrayCopyRet bs f =
+    byteArrayAllocRet (byteArrayLength bs) $ \d -> do
+        withByteArray bs $ \s -> bufCopy d s (byteArrayLength bs)
+        f (castPtr d)
+
 byteArrayCopyAndFreeze :: (ByteArray bs1, ByteArray bs2) => bs1 -> (Ptr p -> IO ()) -> bs2
 byteArrayCopyAndFreeze bs f =
     byteArrayAllocAndFreeze (byteArrayLength bs) $ \d -> do
diff --git a/Crypto/Internal/Memory.hs b/Crypto/Internal/Memory.hs
index f603f94..d72928d 100644
--- a/Crypto/Internal/Memory.hs
+++ b/Crypto/Internal/Memory.hs
@@ -16,6 +16,7 @@ module Crypto.Internal.Memory
     , bytesTemporary
     , bytesCopyTemporary
     , bytesAlloc
+    , bytesAllocRet
     , bytesLength
     , withBytes
     , SecureBytes
@@ -75,6 +76,12 @@ bytesAlloc sz f = do
     withPtr ba f
     return ba
 
+bytesAllocRet :: Int -> (Ptr p -> IO a) -> IO (a, Bytes)
+bytesAllocRet sz f = do
+    ba <- newBytes sz
+    r <- withPtr ba f
+    return (r, ba)
+
 bytesLength :: Bytes -> Int
 bytesLength = sizeofBytes