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index 00000000..d1a566a8
--- /dev/null
+++ b/Cargo.lock
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diff --git a/Cargo.toml b/Cargo.toml
index 3a88876d..bf0c7d8c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,3 +5,6 @@ authors = ["David Craven <david@craven.ch>"]
 edition = "2018"
 
 [dependencies]
+cid = "*"
+multibase = "*"
+multihash = "*"
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 00000000..81d2037e
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,121 @@
+//! IPFS node implementation
+#![deny(missing_docs)]
+#![deny(warnings)]
+use cid::Cid;
+use std::collections::HashMap;
+use std::sync::Arc;
+
+/// Ipfs struct creates a new IPFS node and is the main entry point
+/// for interacting with IPFS.
+pub struct Ipfs {
+    blocks: HashMap<Vec<u8>, Block>,
+}
+
+impl Ipfs {
+    /// Creates a new ipfs node.
+    pub fn new() -> Self {
+        Ipfs {
+            blocks: HashMap::new(),
+        }
+    }
+
+    /// Puts a block into the ipfs repo.
+    pub fn put_block(&mut self, block: Block) -> Result<Cid, ()> {
+        let cid = block.cid();
+        self.blocks.insert(cid.to_bytes(), block);
+        Ok(cid)
+    }
+
+    /// Retrives a block from the ipfs repo.
+    pub fn get_block(&self, cid: &Cid) -> Result<Block, ()> {
+        self.blocks.get(&cid.to_bytes())
+            .map_or(Err(()), |block| Ok((*block).clone()))
+    }
+}
+
+#[derive(Clone, Debug, PartialEq)]
+/// An immutable ipfs block.
+pub struct Block {
+    content: Arc<Vec<u8>>,
+}
+
+impl Block {
+    /// Creates a new immutable ipfs block.
+    pub fn new(content: Vec<u8>) -> Self {
+        Block { content: Arc::new(content) }
+    }
+
+    /// Returns the size of the block in bytes.
+    pub fn size(&self) -> usize {
+        self.content.len()
+    }
+
+    /// Returns the content id of the block.
+    pub fn cid(&self) -> Cid {
+        let prefix = cid::Prefix {
+            version: cid::Version::V0,
+            codec: cid::Codec::DagProtobuf,
+            mh_type: multihash::Hash::SHA2256,
+            mh_len: 32,
+        };
+        Cid::new_from_prefix(&prefix, &self.content)
+    }
+}
+
+impl From<&str> for Block {
+    fn from(content: &str) -> Block {
+        Block::new(content.as_bytes().to_vec())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_raw_block_cid() {
+        let content = "hello\n".as_bytes();
+        let cid = "zb2rhcc1wJn2GHDLT2YkmPq5b69cXc2xfRZZmyufbjFUfBkxr";
+        let prefix = cid::Prefix {
+            version: cid::Version::V1,
+            codec: cid::Codec::Raw,
+            mh_type: multihash::Hash::SHA2256,
+            mh_len: 32,
+        };
+        let computed_cid = Cid::new_from_prefix(
+            &prefix,
+            &content,
+        ).to_string();
+        assert_eq!(cid, computed_cid);
+    }
+
+    #[test]
+    fn test_dag_pb_block_cid() {
+        let content = "hello\n".as_bytes();
+        let cid = "QmUJPTFZnR2CPGAzmfdYPghgrFtYFB6pf1BqMvqfiPDam8";
+        let prefix = cid::Prefix {
+            version: cid::Version::V0,
+            codec: cid::Codec::DagProtobuf,
+            mh_type: multihash::Hash::SHA2256,
+            mh_len: 32,
+        };
+        let computed_cid = Cid::new_from_prefix(
+            &prefix,
+            &content,
+        ).to_string();
+        assert_eq!(cid, computed_cid);
+    }
+
+    #[test]
+    fn test_put_and_get_block() {
+        let mut ipfs = Ipfs::new();
+        let block = Block::from("hello block\n");
+        assert_eq!(block.cid().to_string(),
+                   "QmVNrZhKw9JwYa4YPEZVccQxfgQJq993yP78QEN28927vq");
+        assert_eq!(block.size(), 12);
+
+        let cid = ipfs.put_block(block.clone()).unwrap();
+        let new_block = ipfs.get_block(&cid).unwrap();
+        assert_eq!(block, new_block);
+    }
+}