Replay Attack

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A replay attack is a form of network attack in which a valid data transmission is maliciously or fraudulently repeated or delayed. This is carried out either by the originator or by an adversary who intercepts the data and retransmits it, possibly as part of a masquerade attack by IP packet substitution (such as stream cipher attack). Suppose Alice wants to prove her identity to Bob. Bob requests her password as proof of identity, which Alice dutifully provides (possibly after some transformation like a hash function); meanwhile, Eve is eavesdropping the conversation and keeps the password. After the interchange is over, Eve connects to Bob posing as Alice; when asked for a proof of identity, Eve sends Alice's password read from the last session, which Bob accepts.