Signing authority is the cryptographic permission or control that allows a blockchain transaction to be approved and broadcast. In practice, it is tied to the private key, multisignature policy, hardware signer, or authorization workflow that can produce a valid signature for transfer.
This matters because whoever controls the signing authority can move funds. Attackers often aim at wallet infrastructure, key material, or approval systems rather than the blockchain itself, since stealing signing power can drain a hot wallet quickly. Defenders reduce risk by separating signing authority from public services, using multisig or hardware security modules, limiting withdrawals, logging approvals, and rotating or revoking credentials after suspected compromise.