The revelation of two new attacks in the past month has tightened the noose around the Internet TLS system. These attacks can retrieve passwords, credit card numbers, and other sensitive data from certain transmissions protected by secure sockets layer and transport layer security protocols.
Both attacks targeted the RC4 stream cipher, which is estimated to encrypt about 30% of today's TLS traffic. The result of the attack revealed small portions of the plaintext within an HTTPS-encrypted data stream. It allowed the attackers to see more than 17 billion (234) separate encryptions of the same data. This set the bar high, given that the attack only revealed a small portion of the plaintext. Once the researchers demonstrated that the attack could decrypt HTTPS-protected authentication cookies, which are used to access email , Google and other website operators immediately took notice.
Now, researchers have identified some improvements that will allow them to recover RC4-protected passwords, with a 50% success rate and more than 67 million (226) encryptions. The exploits, published last week in a paper titled Attacks Only Get Better: Password Recovery Attacks Against RC4 in TLS , concern both basic authentication over HTTPS and the IMAP protocol widely used for retrieving and storing email.
A second exploit targeting RC4 was devised by researchers at security firm Imperva and presented last Thursday at the Black Hat security in Singapore. The attack uses new ways to exploit the “invariance weakness,” a key pattern in RC4 keys that can leak plaintext data into ciphertext under certain conditions. The aforementioned vulnerability first came to light in 2001. Given the age of the vulnerability, the Imperva researchers renamed the new exploit the “bar-mitzvah attack.”
