Message authentication

#This application was originally filed as PCT Application No. PCT/FI2015/050701 filed Oct. 16, 2015.

#The present application relates to the field of message authentication, for example in a wireless environment.

#In electronic communication, such as wire-line or wireless electronic communication, ensuring message authenticity may be of high importance. For example, when communicating sensitive information, such as information relevant to health, personal finances, personal communication, corporate plans, unreleased corporate financial results or information relating to public safety, message authenticity may be an important requirement. Furthermore, even when communicating only to cause electrically locked doors to open, for example, authentication of packet origin may be important to prevent unauthorized persons from passing through the doors.

#FIG. 1 illustrates a system in accordance with at least some embodiments of the present invention;

#FIG. 2 illustrates a message format in accordance with at least some embodiments of the present invention;

#FIG. 3 illustrates an example apparatus capable of supporting at least some embodiments of the present invention;

#By including in a message a protection bit sequence, such as a counter or a timestamp, divided into two parts, authentication of the message may be facilitated. In detail, a first part of the protection bit sequence may be provided in the message in both plaintext, that is, unencrypted, format and in encrypted format. A second part of the protection bit sequence may be provided elsewhere in the message, for example in unencrypted format. Thus a receiver that is in possession of a collection of secret keys may try the secret keys in turn, to find out which one was used to encrypt the plaintext format first part of the protection bit sequence in the message into the encrypted format first part of the protection bit sequence in the message. The identified secret key is associated with a sender identity, which is then taken as an identity of a node that sent the message. A sender address field may be used, at least in part, for the protection bit sequence, in other words, a sender address field may be set, at least in part, to a part of the protection bit sequence.

#The protection bit sequence, both parts together, may be incrementing between messages from the same sender, to protect against replay attacks. Authenticating the message may further comprise checking the protection bit sequence in the message, comprising both parts, is incremented with respect to a preceding, for example a sequentially immediately preceding, message from the same recipient. Herein the term incrementing may also, where applicable, refer to decrementing, which are both examples of advancing.

#FIG. 1 illustrates a system in accordance with at least some embodiments of the present invention. The system of FIG. 1 comprises device 110, which may comprise, for example, an electrical key device, a personal device, a cellular telephone, a smartphone, a phablet device, a tablet computer, a laptop computer, a desktop computer or another kind of suitable device, for example. Device 110 may be configured to transmit messages. Such messages may be formatted according to a predefined scheme, for example, into data structures that comprise one or a plurality of bit fields. The bit fields may be of predetermined lengths, for example 32 bits, 8 bits or 160 bits. The bit fields may be of differing lengths with respect to each other.