diem / ledger-nano-app

Note to readers: Silvergate Capital Corporation announced in January 2022 that it acquired intellectual property and other technology assets related to running a blockchain-based payment network from Diem, further investing in its platform and enhancing its existing stablecoin infrastructure.

---

Diem Core implements a decentralized, programmable distributed ledger which provides a financial infrastructure that can empower billions of people.

Note to Developers

• Diem Core is a prototype.
• The APIs are constantly evolving and designed to demonstrate types of functionality. Expect substantial changes before the release.
• We’ve launched a testnet that is a live demonstration of an early prototype of the Diem Blockchain software.

Quick Links

Learn About Diem

• Diem Protocol: Key Concepts
• Life of a Transaction
• JSON-RPC API Specification
• JSON-RPC SPEC

Getting Started - Try Diem Core

• My First Transaction
• Getting Started With Move

Technical Papers

• The Diem Blockchain
• Move: A Language With Programmable Resources
• State Machine Replication in the Diem Blockchain

Governance

• Diem Improvement Proposals

Blog

• Diem: The Path Forward

License

Diem Core is licensed as Apache 2.0.

ledger-nano-app's Issues

Parse a bcs serialized RawTransaction and return important fields

When a RawTransaction is being signed on the ledger nano device, we want to display relevant transaction fields on the display so that the user can confirm them before signing.

Source of RawTransaction struct : https://github.com/diem/diem/blob/0bf8a9702c847bb9741b3b4747ed4e0ca5f1a827/types/src/transaction/mod.rs#L67

Fields that we want to extract:

• sequence_number: u64
• payload: TransactionPayload
  • If payload is of type ScriptFunction(ScriptFunction), parse
    • module: ModuleId,
    • function: Identifier,
    • ty_args: Vec,
    • args: Vec<Vec>,

Example serialized (hex-encoded) RawTransaction in bcs is:

000000000000000000000000000000016d0500000000000003000000000000000000000000000000010e5061796d656e74536372697074731a706565725f746f5f706565725f776974685f6d657461646174610107000000000000000000000000000000010358555303585553000410000000000000000000000000000000dd0801000000000000000100010048010000000000009b0300000000000003585553287412000000000004

The code for constructing this RawTransaction object and serializing it is here : https://github.com/ankushagarwal/libra/blob/test-txn-serialize/api/src/tests/transactions_test.rs#L1701

We need to take this serialized RawTransaction in our app and write a function which can extract the fields mentioned above

Step 1

Write a function in rust-app/src/utils.rs which takes as an input the raw_txn as a byte array (&[u8]) and parses returns the u64 sequence number.

Sample fn signature : fn seq_num(raw_txn: &[u8]) -> Result<u64, u8>