Multi-signature, often abbreviated as multi-sig, is a security measure used in various contexts, including cryptocurrencies, cloud storage, and other digital transactions, where multiple parties must provide their approval or signatures before a transaction or action can be executed. The categories of multi-signature can be broadly classified based on the number of signatures required and the type of participants involved:
Threshold Signatures: In this category, a pre-defined number or threshold of signatures is required to authorize a transaction. For example, a 2-of-3 multi-sig wallet requires any two out of three authorized parties to sign off on a transaction before it can be processed.
M-of-N Signatures: This is a specific type of threshold signature where 'M' represents the number of signatures needed, and 'N' is the total number of possible signatories. For instance, a 3-of-5 setup means that any three signatures from a group of five people are sufficient to approve a transaction.
Hierarchical Deterministic (HD) Multi-signature: This type allows for the creation of an unlimited number of addresses from a single seed phrase, with each address being controlled by a different subset of signatories. It is commonly used in cryptocurrency wallets to enhance security and privacy.
Distributed Multi-signature: In this setup, the responsibility for signing transactions is distributed across multiple, geographically dispersed parties. This can enhance security by ensuring that no single point of failure exists.
Cross-Entity Multi-signature: This involves multiple entities or organizations each holding a part of the signature required to complete a transaction. It is often used in business settings where multiple parties need to agree on a financial transaction.
In the context of cloud services, multi-signature can be implemented to secure access and control over cloud resources. For example, Tencent Cloud offers a feature called "Multi-Factor Authentication (MFA)" which, while not exactly multi-signature, adds an additional layer of security by requiring users to provide two or more verification factors to gain access to a resource such as an application, online account, or a VPN. This can be seen as a form of multi-signature in the broader sense of requiring multiple forms of verification for access approval.