I am very new to cryptography but can someone explain what exactly does
1...1 mean in general term. Is it that 1st and last bit can be
0,0 and `1,1 respectively and in-between bits can be anything $(0,1)$?
In case it helps… I stumbled upon this while trying to solve the following multiple choice question:
Let F be a block cipher with n-bit block length. Consider the message authentication code for 2n-bit messages defined by Mack(m1,m2)=Fk(m1⊕m2). Which of the following gives a valid attack on this scheme?
- Obtain tag t on message m,0…0 (with m≠0…0), and then output the tag t on the message 0…0,0…0.
- Obtain tag t on message m1,m2 (with m1≠m2), and then output the tag t on the message m2,m1.
- Obtain tag t on message m,0…,0, and then output the tag t⊕(1…1) on the message m,1…1.
- Obtain tag t on message m,m, and then output the tag 0…0 on the message 0…0,m.
Please note that I do not want an answer to the multiple choice question. I merely want to know how to interpret the notation