diff --git a/src/filter.rs b/src/filter.rs
new file mode 100644
index 000000000..92e953c04
--- /dev/null
+++ b/src/filter.rs
@@ -0,0 +1,49 @@
+//! multilevel bloom filter interface
+use hash::*;
+use std::collections::HashMap;
+
+/// Represents bloom index in cache
+/// 
+/// On bloom level 0, all positions represent different blooms. 
+/// On higher levels multiple positions represent one bloom
+/// and should be transformed to `BlockIndex` to get index of this bloom
+#[derive(Eq, PartialEq, Hash)]
+pub struct BloomIndex {
+	level: u8,
+	level_index: usize,
+	index: usize,
+}
+
+pub trait FilterDataSource {
+	/// returns reference to log at given position if it exists
+	fn bloom_at_index(&self, index: &BloomIndex) -> Option<&H2048>;
+}
+
+pub trait Filter: Sized {
+	/// creates new filter instance
+	fn new<T>(data_source: &T, index_size: usize, levels: u8) -> Self where T: FilterDataSource;
+
+	/// converts block number and level to `BloomIndex`
+	fn bloom_index(&self, block_number: usize, level: u8) -> BloomIndex;
+
+	/// add new bloom to all levels 
+	fn add_bloom(&self, bloom: &H2048, block_number: usize) -> HashMap<BloomIndex, H2048>;
+
+	/// add new blooms starting from block number
+	fn add_blooms(&self, blooms: &[H2048], block_number: usize) -> HashMap<BloomIndex, H2048>;
+
+	/// reset bloom at level 0 and forces rebuild on higher levels
+	fn reset_bloom(&self, bloom: &H2048, block_number: usize) -> HashMap<BloomIndex, H2048>;
+
+	/// sets lowest level bloom to 0 and forces rebuild on higher levels
+	fn clear_bloom(&self, block_number: usize) -> HashMap<BloomIndex, H2048>;
+
+	/// returns numbers of blocks that may contain Address
+	fn blocks_with_address(&self, address: &Address) -> Vec<usize>;
+
+	/// returns numbers of blocks that may contain Topic
+	fn blocks_with_topics(&self, topic: &H256) -> Vec<usize>;
+
+	/// returns numbers of blocks that may log bloom
+	fn blocks_with_bloom(&self, bloom: &H2048) -> Vec<usize>;
+}
diff --git a/src/lib.rs b/src/lib.rs
index acb03afb5..7ebf91f51 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -21,6 +21,7 @@ pub mod sha3;
 pub mod hashdb;
 pub mod memorydb;
 pub mod math;
+pub mod filter;
 
 //pub mod network;