Patent ID: 8868911

Claim:
A member authentication method for a dynamic group, whereby a first member authenticates a second member, comprising Step (a): said first member encrypting a first authentication message into an encrypted first authentication message and sending said encrypted first authentication message to said second member; Step (b): said second member decrypting said encrypted first authentication message into a once-decrypted first authentication message, generating a second authentication message, encrypting said once-decrypted first authentication message and said second authentication message into an encrypted once-decrypted first authentication message and an encrypted second authentication message, and sending said encrypted once-decrypted first authentication message and said encrypted second authentication message to said first member; Step (c): said first member decrypting said encrypted once-decrypted first authentication message and said encrypted second authentication message into a twice-decrypted first authentication message and a once-decrypted second authentication message, and comparing said twice-decrypted first authentication message with said first authentication message, wherein if said twice-decrypted first authentication message is different from said first authentication message, authentication fails, and wherein if said twice-decrypted first authentication message is identical to said first verification message, execute Step (d); Step (d): said first member encrypting a comparison result and said once-decrypted second authentication message into an encrypted comparison result and an encrypted once-decrypted second authentication message, and sending said encrypted comparison result and said encrypted once-decrypted second authentication message to said second member; and Step (e): said second member decrypting said encrypted comparison result and said encrypted once-decrypted second authentication message to obtain said comparison result and a twice-decrypted second authentication message, and comparing said twice-decrypted second authentication message with said second authentication message, wherein if said twice-decrypted second authentication message is different from said second authentication message, authentication fails, and wherein if said twice-decrypted second authentication message is identical to said second authentication message, authentication succeeds.