Vulnerabilidade no SSL/TLS

Aliás no algoritmo RC4, que é usado no SSL/TLS. A solução é não usar o RC4:


HTTPS Security Encryption Flaws Found
InformationWeek

The flaw exists in the RC4 encryption algorithm that's often used to help secure the SSL/TLS communications that underpin secure (HTTPS) Web pages. The flaw was first disclosed last week by University of Illinois at Chicago professor Dan Bernstein at the Fast Software Encryption conference in Singapore, in a talk titled "Failures of secret-key cryptography" that's based on research he conducted with researchers from University of London's Royal Holloway and the Eindhoven University of Technology in the Netherlands.

"The transport layer security (TLS) protocol aims to provide confidentiality and integrity of data in transit across untrusted networks like the Internet," according to the group's research presentation. "It is widely used to secure Web traffic and e-commerce transactions on the Internet."

But RC4, the researchers found, isn't sufficiently random, and with enough time and effort, an attacker could recover some plaintext from a communication secured using TLS and RC4. "We have found a new attack against TLS that allows an attacker to recover a limited amount of plaintext from a TLS connection when RC4 encryption is used," they said. "The attacks arise from statistical flaws in the keystream generated by the RC4 algorithm, which become apparent in TLS ciphertexts when the same plaintext is repeatedly encrypted at a fixed location across many TLS sessions."

The vulnerability has wide-ranging repercussions, given current RC4 use. "Around 50% of all TLS traffic is currently protected using the RC4 algorithm," they said. "It has become increasingly popular because of recent attacks on CBC-mode encryption on TLS, and is now recommended by many commentators." Those CBC-mode encryption attacks have included padding oracle attacks, the BEAST attack against browsers and the Lucky 13 attack that was first disclosed last month.

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