GitHub Logo HIP-323: C SDK

Author Greg Scullard, Romain Menetrier
Working Group Greg Scullard, Romain Menetrier
Status Accepted
Needs Council Approval No
Review period ends Tue, 01 Feb 2022 07:00:00 +0000
Type Standards Track
Category Application
Created 2021-12-09


This HIP concerns the creation of a C SDK which is currently missing from the family of Hedera SDKs. There is a .NET SDK that supports C#. However, in IoT, a native C implementation is often a requirement.


As IoT projects take hold, particularly in the field of sustainability, an SDK that is easy to use in IoT development environments is highly desirable. A C SDK would also be preferred by many gaming solutions.


While the initial impetus behind a C SDK was born from an IoT mindset, the SDK should be usable in all contexts and not limited to a particular desktop or IoT chipset.

A .NET SDK exists, which enables development in C#, however in the context of IoT or non-Microsoft platforms, this requires the use of abstraction layers which may not always be fully compatible with the target platform and may result in heavier/more complex binaries.

User stories

As a C developer, I want to use the SDK to build solutions natively in C that can interact with Hedera.

As an IoT developer, I want to be able to deploy code to my IoT platform regardless of my choice of architecture (ARM, ESP…) so that my device can interact with Hedera.

As a game developer, I want to be able to build a game natively in C such that it can interact with Hedera.

As a C developer, I want to be able to leverage all of Hedera’s Services (Crypto, Consensus, Files, Tokens, Smart Contracts).


  • The C SDK must be open source under the Apache 2.0 license
  • The C SDK must follow existing SDK conventions to ease developer adoption and documentation
  • The C SDK must have feature-parity with other SDKs and include HIPs that are under development or to be approved
  • The C SDK must include examples for developers to get started with minimal effort
  • The C SDK must be cross-platform, meaning compilation can be targeted towards IOT devices (any architecture) as well as desktop environments
  • The C SDK must enable signing for transactions using private keys, including key lists and threshold keys
  • The C SDK must support external signing through a custom implementation such as a Hardware Signing Module, which is not embedded in the SDK itself. The SDK should present the equivalent of an interface/specification for the custom implementation to adhere to
  • The C SDK must support a list of nodes to submit transactions to at random
  • The C SDK must implement an appropriate retry mechanism in the event a node is temporarily unavailable
  • The C SDK must implement the generation of new private keys, as well as the recovery of existing keys from mnemonics or a string representation of the key
  • The C SDK must implement getting Receipts and Records (and the associated error handling and retry/timeout)
  • The C SDK must support the Crypto Service (Create Account, Transfer, etc…)
  • The C SDK must support the Consensus Service (Create Topic, Submit message, etc…)
  • The C SDK must support the File Service (Create File, Append to File, Get File Contents, etc…)
  • The C SDK must support the Token Service (Create fungible token, Create non-fungible token, Mint token, Transfer token, etc…)
  • The C SDK must support the Smart Contract Service (Create Contract, Call Contract, Local Call, etc…)
  • The C SDK must support mirror subscriptions for HCS topic messages

Backwards Compatibility

None at this stage.

Security Implications

None at this stage.

How to Teach This

The SDK will include code examples for developers new to the SDK to quickly familiarise themselves with it, for example:

  • Creating an account
  • Making a HBAR transfer
  • Getting a receipt for a transaction

Reference Implementation

None at this stage.

Rejected Ideas


Open Issues



Java SDK as inspiration for the C SDK


This document is licensed under the Apache License, Version 2.0 – see LICENSE or (


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