Successful Authentication/Identification
One Time Password
• Shared secret list
A one-time password (OTP) is an automatically generated numeric or alphanumeric string of characters that authenticates the user for a single transaction or session.
L-2 P.10
One-Time Pads
Large, non-repeating set of keys
Used by sender exactly once, then destroyed
Considered to be “the perfect cipher”
Receiver must have pad identical to sender
Typically used with a Vigenère tableau
• Vigenère tableau is a way of doing a different substitution for EVERY different letter.
Two potential problems - the need for:
• Absolute synchronization between sender and receiver
• Unlimited number of keys
Book Cipher
• Usually an adequate substitute for a one-time pad
• Number of keys is only limited by the length of the book
• Receiver and sender must:
Have the same edition of the book
Use the same Vigenère tableau
Use a different starting point every day, until the whole book is used up