Problem

There is currently no native support in the Hedera C++ SDK for signing transactions using only the raw bodyBytes. This presents a challenge when integrating with Hardware Security Modules (HSMs), which securely hold private keys and only allow signing of raw byte messages. C++ is often written in lower layers and HSM signing could prove useful when using embedded devices or other hardware layer agents.

This request stems from a real-world integration scenario described in hiero-ledger/hiero-sdk-js#3037, where the need is to:

• Create and freeze a transaction.
• Serialize the transaction to bodyBytes.
• Send the serialized bytes to an HSM for signing.
• Reconstruct the transaction and manually add the signature.
• Submit the signed transaction to the Hedera network.

Solution

Add native support for manual HSM-based transaction signing in the SDK.

Alternatives

No response