BSN Book (#107)

* fix link in readme

* update overview in book

* Nits, making corrections to naming, and increase accuracy of statements

---------

Co-authored-by: Brandon Roberts <[email protected]>

README.md

@@ -12,7 +12,7 @@
 
 ## Overview
 
-`blobstream_sn` is a port of Celestia Blobstream X [contracts](https://github.com/celestiaorg/blobstream-contracts)
+`blobstream_sn` is a port of Celestia Blobstream X [contracts](https://github.com/succinctlabs/blobstreamx)
 in [Cairo](https://book.cairo-lang.org/) for [Starknet](https://starknet.io/).
 
 See the book to dive down the [blobhole...](https://blobstream-stark.net)

book/src/overview/README.md

@@ -2,15 +2,64 @@
 
 ![BSN Module](../assets/blobstreamSnModule.png)
 
-Blobstream allows Celestia block header data roots to be relayed
-***from Celestia to Starknet.***
+Blobstream Starknet integrates Celestia's modular Data Availability layer with
+Starknet, allowing L3s and dapps to submit DA to Celestia and then verify DA on
+Starknet through Blobstream.
 
-It does not support bridging assets such as fungible
-or non-fungible tokens directly, and cannot send messages from the Starknet
-back to Celestia.
+## Blobstream : Modular Data Availability Layer
 
-`blobstream_sn` is a port of Celestia Blobstream in Cairo deployed on Starknet:
+[Blobstream](https://blog.celestia.org/introducing-blobstream/) is a solution
+developed by Celestia Labs to stream Celestia's modular DA layer to Ethereum.
+Blobstream relays commitments of Celestia's data root using an on-chain light
+client. This enables Ethereum developers to create scalable L2s.
 
-- [Solidity Blobstream Contracts](https://github.com/celestiaorg/blobstream-contracts)
+Celestia is based on Data Availability Sampling (DAS), which allows any user
+to contribute to DA for rollups by running a sampling light node. As the light
+node network grows, Celestia can scale without compromising security for end users.
+
+To optimize Celestia as a DA layer, Succinct Labs contributed **Blobstream X**,
+a zero-knowledge (ZK) implementation that uses a ZK light client to verify
+Celestia validator signatures on-chain with a single ZK proof. This approach
+reduces overhead for validators, simplifies the core Celestia protocol, and
+enables faster streaming of data root commitments for Ethereum L2s.
+
+## Why Starknet L3s should use Celestia
+
+Several key differences highlight the advantages of using Celestia for DA.
+
+### Scalability
+
+With a modular approach to DA, Celestia maximizes data throughout by providing
+dedicated blobspace that is priced independently of Ethereum gas costs and
+unrelated execution. Also, by taking advantage of [DAS and erasure codings](https://hackmd.io/@vbuterin/sharding_proposal),
+Celestia nodes can verify DA without checking all of the blob data posted.
+
+### Decentralization and Transparency
+
+Other DA solutions, such as [Data Availability Committees](https://celestia.org/glossary/data-availability-committee/),
+introduce significant trust assumptions and liveness issues. This includes
+relying on a small committee of nodes to not withhold data. Celestia decentralizes
+the process by introducing a POS network where light nodes can detect if up to
+two-thirds of validators withhold data or produce invalid blocks, holding them
+accountable via slashing.
+
+## How does it work
+
+The Blobstream Starknet contracts are ported into Cairo from their
+[Solidity counterparts](https://github.com/succinctlabs/blobstreamx), allowing
+for more efficient and STARK-friendly execution.
+
+L3s using Blobstream for DA verification must deploy a [core contract](./l3_starknet/core_contract.md)
+onto Starknet L2. Starknet-like L3s could use [piltover](https://github.com/keep-starknet-strange/piltover),
+a Cairo port for Starknet's L1 core contract.
+
+Then the Starknet L3 can use Celestia as DA by :
+
+- Posting blob data to Celestia
+- Verifying the blobs DA on L2 via the [BlobstreamX contract](https://github.com/keep-starknet-strange/blobstream-starknet/blob/main/src/lib.cairo)
+
+Useful links :
+
+- [Solidity Blobstream X Contracts](https://github.com/succinctlabs/blobstreamx)
 - [Cairo](https://book.cairo-lang.org/)
 - [Starknet](https://docs.starknet.io/documentation)