Archivo de la etiqueta: cryptography

Using secure pseudonymous identifiers to protect identification numbers

By now you probably have read of the Equifax data leakage. This reminded me of the idea of secure pseudonymous identifiers I had been thinking on for some time. Secure pseudonymous identifiers make use of cryptography to make it hard or impossible to recover the original identifiers representing a specific person. To be sincere, I wouldn’t be surprised if somebody else came with this idea first and named it something else since it’s quite simple. Sadly, I really haven’t had the time to check that out.

In this article I will introduce the concept of identifiers then pseudonymous identifiers and finally secure pseudonymous identifiers. I will also explain why they are a very useful technique to deter the risk of leakage on data whose only purpose is identifying an individual like U.S.A.’s SSN numbers or Spanish ID card numbers among others.

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Cryptanalyzing Petya

A few days ago, leo-stone reverse-engineered the Petya ransomware and found that it was possible to use genetic algorithms to find out the key. He even published a nice decrypting tool in go. I took his globe and decided to prove why this is mostly a specific issue of how Petya reduced Salsa-20 to use only 16 bit words.

In this blogpost I’ll do a cryptanalysis of the Petya encryption algorithm (as published by leo-stone) and reduce the key entropy so that a single known plaintext is enough to break the algorithm. I’ll also explain how to use these results to make a faster and more efficient decrypting tool. And finally I’ll explain why genetic algorithms as used by leo-stone worked.

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