eciesjs

noble cryptography is a family of minimal-dependency TypeScript cryptographic libraries that prioritize readable source, signed releases, and transparent npm builds, and they underpin most modern JavaScript wallets including MetaMask, Rabby, Rainbow, and many SDKs across the ecosystem.

Web3Signer is a remote signing service that keeps keys in a vault or hardware security module. Node and validator operators run it so signing happens outside the client process.

The Fireblocks SDK connects applications to Fireblocks' MPC wallet infrastructure for signing, transfers, and treasury operations. Builders use it to automate transactions and approval policies for wallets managed through Fireblocks.

Turnkey offers an API and SDK for secure key generation and transaction signing backed by trusted execution environments. Builders use it to create and operate wallet infrastructure without holding raw private keys in their own code.

Lit Protocol is a decentralized network for threshold key management with programmable signing through its programmable key pairs. Builders use its SDK when signing or decryption should follow rules enforced by a network rather than a single key holder.

eth-keys is a Python library for secp256k1 keys and signatures, and it sits under eth-account and web3.py. Python builders import it when they need key and signature operations directly.