diff --git a/Data/ASN1/BitArray.hs b/Data/ASN1/BitArray.hs
--- a/Data/ASN1/BitArray.hs
+++ b/Data/ASN1/BitArray.hs
@@ -1,15 +1,28 @@
+{-# LANGUAGE DeriveDataTypeable #-}
 module Data.ASN1.BitArray
 	( BitArray(..)
+	, BitArrayOutOfBound(..)
 	, bitArrayLength
 	, bitArrayGetBit
+	, bitArraySetBitValue
+	, bitArraySetBit
+	, bitArrayClearBit
 	, bitArrayGetData
 	, toBitArray
 	) where
 
 import Data.Bits
 import Data.Word
+import Data.Maybe
 import qualified Data.ByteString.Lazy as L
+import Data.Typeable
+import Control.Exception (Exception, throw)
 
+-- | throwed in case of out of bounds in the bitarray.
+data BitArrayOutOfBound = BitArrayOutOfBound Word64
+	deriving (Show,Eq,Typeable)
+instance Exception BitArrayOutOfBound
+
 -- | represent a bitarray / bitmap
 data BitArray = BitArray Word64 L.ByteString
 	deriving (Show,Eq)
@@ -18,12 +31,36 @@
 bitArrayLength :: BitArray -> Word64
 bitArrayLength (BitArray l _) = l
 
+bitArrayOutOfBound :: Word64 -> a
+bitArrayOutOfBound n = throw $ BitArrayOutOfBound n
+
 -- | get the nth bits
 bitArrayGetBit :: BitArray -> Word64 -> Bool
 bitArrayGetBit (BitArray l d) n
-	| n >= l    = error ("array bit out of bounds: requesting bit " ++ show n ++ " but only got " ++ show l ++ " bits")
+	| n >= l    = bitArrayOutOfBound n
 	| otherwise = flip testBit (7-fromIntegral bitn) $ L.index d (fromIntegral offset)
 		where (offset, bitn) = n `divMod` 8
+
+-- | set the nth bit to the value specified
+bitArraySetBitValue :: BitArray -> Word64 -> Bool -> BitArray
+bitArraySetBitValue (BitArray l d) n v
+	| n >= l    = bitArrayOutOfBound n
+	| otherwise =
+		let (before,after) = L.splitAt (fromIntegral offset) d in
+		-- array bound check before prevent fromJust from failing.
+		let (w,remaining) = fromJust $ L.uncons after in
+		BitArray l (before `L.append` (setter w (fromIntegral bitn) `L.cons` remaining))
+		where
+			(offset, bitn) = n `divMod` 8
+			setter = if v then setBit else clearBit
+
+-- | set the nth bits
+bitArraySetBit :: BitArray -> Word64 -> BitArray
+bitArraySetBit bitarray n = bitArraySetBitValue bitarray n True
+
+-- | clear the nth bits
+bitArrayClearBit :: BitArray -> Word64 -> BitArray
+bitArrayClearBit bitarray n = bitArraySetBitValue bitarray n False
 
 -- | get padded bytestring of the bitarray
 bitArrayGetData :: BitArray -> L.ByteString
diff --git a/asn1-data.cabal b/asn1-data.cabal
--- a/asn1-data.cabal
+++ b/asn1-data.cabal
@@ -1,5 +1,5 @@
 Name:                asn1-data
-Version:             0.6.1.2
+Version:             0.6.1.3
 Description:
     ASN1 data reader and writer in raw form with supports for high level forms of ASN1 (BER, CER and DER).
     .