Method and device for authenticating a primary station
The present invention relates to a method for a secondary station to obtain a time reference in a cellular network in order to verify the freshness of received messages. The method comprises the steps of receiving a plurality of system information, SI, messages from a plurality of primary stations, said SI messages including each a respective time reference information related to the corresponding primary station, checking the validity of a received signature for each of the primary stations, checking a cell identifier for each of the primary stations with a valid signature, and ignoring time reference information from primary stations with a cell identifier being identical to another primary station and having an earlier value than the one from the other primary station, and deducing a local time reference from one or more of the time reference information originating from primary stations with a valid signature.
1 . A method for a secondary station to obtain a time reference in a cellular network, the method comprising:
the secondary station at initial connection to the network sending a request for a time reference, said request being addressed to a Signature Generator, and wherein the request for time reference includes a randomly generated number used as a nonce;
receiving the time reference and the nonce, wherein the time reference and the nonce are signed with a nonce signature; and
using the nonce and nonce signature to check authenticity of received messages, and using the received time reference to configure a clock at the secondary station;
receiving, by the secondary station, a plurality of system information (SI) messages from a plurality of primary stations, said SI messages including each a respective time reference information related to the corresponding primary station;
checking the validity of a received signature for each of the primary stations;
checking a cell identifier for each of the primary stations with a valid signature, and ignoring time reference information from primary stations with a cell identifier being identical to another primary station and having an earlier value than the one from the other primary station; and
deducing a local time reference from one or more of the time reference information originating from primary stations with a valid signature.
2 . The method of claim 1 , wherein the time reference information is at least one of the following: a time offset representative of the difference between a clock value at the primary station and a clock value at a Signature Generator of the network, a clock value at the primary station, a clock value at the Signature Generator.
3 . The method of claim 1 , wherein the step of deducing a local time reference includes computing an average from a plurality of the time reference information originating from primary stations with a valid signature and without duplicate cell identifier with earlier time.
4 . The method of claim 1 , wherein the step of deducing a local time reference includes selecting the time reference information with the latest value originating from primary stations with a valid signature.
5 . The method of claim 1 , wherein the request is part of an Initial Radio Resource Communication, RRC, setup request message.
6 . The method of claim 1 , wherein the request is part of a Network Access Stratum (NAS) identity response message sent in response to a NAS identity request.
7 . The method of claim 1 , wherein the received signature is checked using at least one of the following algorithms: a Public Key Infrastructure (PKI) algorithm, a Boneh-Lynn-Shacham (BLS) signing algorithm, a Boneh-Gentry-Lynn-Shacham (BGLS) signing algorithm, an Elliptic Curve Digital Signature Algorithm (ECDSA), Falcon signing algorithm, Rainbow signing algorithm, a Great Multivariate Short Signature (GeMSS) algorithm.
8 . A secondary station adapted for communicating in a network, the secondary station comprising:
a transmitter configured to send at initial connection to the network a request for a time reference, said request being addressed to a Signature Generator, wherein the request for time reference includes a randomly generated number used as a nonce;
a hardware receiver adapted to receive the time reference and the nonce, wherein the time reference and the nonce are signed with a nonce signature,
a controller configured to use the nonce and nonce signature to check authenticity of received messages, and to use the received time reference to configure a clock at the secondary station;
wherein the hardware receiver is further adapted to receive a plurality of system information (SI) messages from a plurality of primary stations, said SI messages including each a respective time reference information related to the corresponding primary station;
wherein the controller is further configured to check the validity of a received signature for each of the primary stations, and to check a cell identifier at least for each of the primary stations with a valid signature, and ignore time reference information from primary stations with a cell identifier being identical to another primary station and having an earlier value than the one from the other primary station; and
wherein said controller is adapted to deduce a local time reference from one or more of the time reference information originating from primary stations with a valid signature.
9 . The secondary station of claim 8 , wherein the time reference information is at least one of the following: a time offset representative of the difference between a clock value at the primary station and a clock value at a Signature Generator of the network, a clock value at the primary station, a clock value at the Signature Generator.
10 . The secondary station of claim 8 , wherein deducing a local time reference comprises computing an average from a plurality of the time reference information originating from primary stations with a valid signature and without duplicate cell identifier with earlier time.
11 . The secondary station of claim 8 , wherein deducing a local time reference comprises selecting the time reference information with the latest value originating from primary stations with a valid signature.
12 . The secondary station of claim 8 , wherein the request is part of an Initial Radio Resource Communication, RRC, setup request message.
13 . The secondary station of claim 8 , wherein the request is part of a Network Access Stratum (NAS) identity response message sent in response to a NAS identity request.
14 . The secondary station of claim 8 , wherein the received signature is checked using at least one of the following algorithms: a Public Key Infrastructure (PKI) algorithm, a Boneh-Lynn-Shacham (BLS) signing algorithm, a Boneh-Gentry-Lynn-Shacham (BGLS) signing algorithm, an Elliptic Curve Digital Signature Algorithm (ECDSA), Falcon signing algorithm, Rainbow signing algorithm, a Great Multivariate Short Signature (GeMSS) algorithm.