Thursday, 21 May 2015

New Encryption Leak Threatens Web Servers And Mail Servers

A well-known cryptography professor has discovered a vulnerability in TLS encrypted connections allowing attackers to web and mail servers to attacks and eavesdropping. The vulnerability by Matthew Green " logjam "named and located in the Diffie-Hellman key exchange , a cryptographic algorithm that Internet protocols can establish an encrypted connection. It is essential for various protocols, including HTTPS, SSH, IPsec, SMTPS and protocols that rely on TLS.

Through the logjam attack attacker can, located between the victim and the Internet is vulnerable TLS connections to a 512-bit encryption downgrade. This allows an attacker to decrypt all the data on the encrypted connection and thus read and adjust. The vulnerability is similar to the FREAK-attack which was unveiled in March. Both vulnerabilities are caused by the US export policy in the early 1990s, making strong encryption could not be exported. Instead, if there is only "export-grade" encryption provided. The encryption keys were allowed in this case only 512 bits in size. However, the logjam-attack is focused on the exchange of keys via the Diffie-Hellman algorithm in place of the RSA-algorithm.

The attack affects all servers that Diffie-Hellman "export" encryption support. According to Green, all modern browsers and 8.4% of the 1 million most visited websites on the Internet vulnerable. The researchers experimented with attacking the most common primes 512-bit Diffie-Hellman used to exchange keys and were thus 80% of the servers with Diffie-Hellman "export" encryption downgrade. An intelligence could crack a 1024-bit prime and thus tapping 18% of encrypted connections from the 1 million most visited websites. Cracking a second prime number would make it possible to monitor 66% of VPN servers and 26% of the SSH servers.

Owners of a mail server or Web server are advised to disable the support of export encryption and generate a unique 2048-bit Diffie Hellman Group. Internet users should install the updates for their browsers as they become available. All suppliers are now working on an update. Finally get the advice to system administrators and developers to ensure that TLS libraries up-to-date and Diffie-Hellman Groups are refused less than 1024 bit.

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