| 摘要 |
<P>PROBLEM TO BE SOLVED: To reduce a verification load in a system that periodically performs radio communication. <P>SOLUTION: Road-side units 2 and 3 share private keys K<SB POS="POST">0</SB>, K<SB POS="POST">1</SB>, ..., K<SB POS="POST">n-1</SB>, K<SB POS="POST">n</SB>produced by repeating mapping with a unidirectional function F for a private key K<SB POS="POST">n</SB>using an image obtained by mapping the private key K<SB POS="POST">i</SB>with the unidirectional function F as a private key K<SB POS="POST">i-1</SB>. The road-side unit 2 first defines a message M<SB POS="POST">1</SB>, a hash value Hash (M<SB POS="POST">2</SB>) of a next transmission message M<SB POS="POST">2</SB>, a private key K<SB POS="POST">0</SB>and the like as transmission data and transmits an anchor frame AP<SB POS="POST">1</SB>comprised of the transmission data and a digital signature. Thereafter, the road-side units 2, 3 alternately transmit in each arrival of a periodical transmission term a normal frame NP comprised of a message M<SB POS="POST">j</SB>((j) is a natural number of 2 to (n)) of the present transmission, a hash value Hash(M<SB POS="POST">j+1</SB>) of a next transmission message M<SB POS="POST">j+1</SB>, a message authenticator MAC<SB POS="POST">kj</SB>(M<SB POS="POST">j</SB>, Hash(M<SB POS="POST">j+1</SB>) produced using a private key K<SB POS="POST">j</SB>and a private key K<SB POS="POST">j-1</SB>. <P>COPYRIGHT: (C)2012,JPO&INPIT |
