Transaction signing utilizing asymmetric cryptography

A system comprising:

• a server computer comprising a processor and a computer readable medium memory storing instructions and a centralized transaction verification and accounting module (TVAM) configured to manage private and public key pairs of accounts in a private ledger, wherein a public key associated with a user in the private ledger is configured to be updatable;
• and
• an access device comprising a processor and a computer readable medium storing instructions and a processing module;
• the system configured to implement a method comprising:
• providing, on a device communication interface of the access device that is a point of sale device at a location of a merchant, transaction data to a user device that is a payment device associated with the user,
• wherein the user device signs the transaction data,
• wherein the access device further comprises a network interface configured for communication with the centralized transaction verification and accounting module (TVAM);
• receiving, by the access device, the signed transaction data signed by the user device and a public key of the user from the user device, wherein the access device is configured to use the public key of the user;
• generating, by the processing module of the access device, an authorization request message including the signed transaction data signed by the user device and the public key of the user, wherein the authorization request message that is constructed includes data identifying the authorization request message as corresponding to a signed transaction;
• and
• transmitting, by the access device, the generated authorization request message including the signed transaction data and the public key of the user to the server computer,
• wherein an issuer account identifier associated with the payment device is configured to be accessed from the private ledger managed by the TVAM based on the signed transaction data signed by the user device;
• receiving, by the server computer, the generated authorization request message from the access device;
• determining, by the server computer, that the public key of the user in the received authorized request message matches the public key associated with the user in the private ledger, wherein the private ledger comprises a plurality of public keys and an account balance associated with each of the plurality of public keys;
• determining, by the server computer, that the signed transaction data was signed using a private key of the user and that a current balance associated with the public key of the user is sufficient for authorizing the signed transaction;
• in response to determining that the signed transaction data was signed using the private key of the user and that the current balance associated with the public key of the user is sufficient for authorizing the signed transaction, sending, by the server computer to the access device, an authorization response message indicating that the signed transaction is authorized, wherein the authorization response message for the signed transaction does not include sensitive information;
• and
• updating, by the server computer, the current balance associated with the public key of the user in the private ledger.