Signatures

It is notable that, although when encrypting data to send it to a given recipient, the private key is used for decryption, it is generally possible to do the reverse. For cryptographic signing, private keys are used to generate a signature that can be decrypted (verified) with the public key published for a given user. This inverted use of public-key cryptography allows for users to publish a message in the clear with a high degree of certainty that the signer is the one who wrote it. This again invokes the concept of integrity—if signed by the user’s private key, a message (or transaction) can be assumed to be authentic. Typically, where Blockchains are concerned, when a user wishes to transfer tokens, they sign the transaction with the private key of the wallet. The user then broadcasts that transaction.

It is now also fairly common to have multisignature wallets, and, in that instance, a transaction is most often signed by multiple users and then broadcast, either in the web interface of a hosted wallet service, or in a local client. This is a fairly common use case with software projects with distributed teams.