Secure token transaction unit, secure token reference register, electronic payment transaction system and method for securing a transaction

A token reference register within an electronic payment transaction system, the secure token reference register comprising:

• a secure memory for storing registered token references;
• a secure communication interface for receiving and sending data to one or more secure token transaction units of the electronic payment transaction system;
• a control module which is configured to
• receive one or more replacement requests from the one or more secure token transaction units, wherein each one of the one or more replacement requests comprises an input token reference, an intermediate token reference and/or a partner token reference, wherein the input token reference is the same in each replacement request of a respective secure token transaction unit of the one or more secure token transaction units;
• selectively store the partner token reference of at least one of the one or more replacement requests in the secure memory;
• and
• send at least one replacement request confirmation corresponding to the one or more replacement requests to the respective secure token transaction unit.

A method for securing a transaction of a central bank digital currency token in an electronic payment transaction system, the electronic payment transaction system comprising at least two secure token transaction units and a token reference register, the method comprising:

• generating, for a first transaction according to which an input token stored in the secure memory is transformed to a first intermediate token and a first partner token, a first replacement request, wherein the first intermediate token is a token having a temporary character as it may be overridden by a next transaction before being registered in the electronic payment transaction system via the first replacement request;
• generating, related to the first transaction, a token record, in which the first intermediate token and the first replacement request are stored;
• and
• updating, related to a second transaction, the token record by substituting the first replacement request by a second replacement request for the input token.