Which of the following are MOST susceptible to birthday attacks?

3 thoughts on “Which of the following are MOST susceptible to birthday attacks?”

1. Answer is: Hash passwords thus A is the correct answer:
   The birthday attack is used to create hash collisions. Just like matching any birthday is easier, finding any input that creates a colliding hash with any other input is easier due to the birthday attack. Birthday attacks are based on a unique problem with hashing algorithms based on a concept called the Birthday Paradox.

   https://www.sciencedirect.com/topics/computer-science/birthday-attack#:~:text=Birthday%20attacks%20are%20based%20on,concept%20called%20the%20Birthday%20Paradox.&text=It%20is%20possible%20to%20precompute,determine%20if%20any%20collisions%20occur.

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2. Digital certificates

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3. From https://www.geeksforgeeks.org/birthday-attack-in-cryptography/

   Digital signature susceptibility –
   Digital signatures can be susceptible to birthday attack. A message m is typically signed by first computing H(m), where H is cryptographic hash function, and then using some secret key to sign H(m). Suppose Alice want to trick Bob into signing a fraudulent contract. Alice prepare a fair contract m and fraudulent one m’. She then finds a number of positions where m can be changed without changing the meaning, such as inserting commas, empty lines, one versus two spaces after a sentence, replacing synonyms etc. By combining these changes she can create a huge number of variations on m which are all fair contracts.

   Similarly, Alice can also make some of these changes on m’ to take it even more closer towards m, that is H(m) = H(m’). Hence, Alice can now present the fair version m to Bob for signing. After Bob has signed, Alice takes the signature and attaches to it the fraudulent contract. This signature proves that Bob has signed the fraudulent contract.

   To avoid such an attack the output of hash function should be a very long sequence of bits such that birthday attack now becomes computationally infeasible.

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