The Internet encryption protocol TLS (Transport Layer Security) is being modified. Involved in attacks, researchers and IT experts have now contributed to revealing serious security gaps in the protocol.
The researchers have succeeded in stealing a key that two parties had negotiated via TLS version 1.2. This kind of a key is required when communication parties want to exchange secret information – customer transmitting credit card details to an online shop, for example. In this case, TLS protocol provides three approaches for negotiating keys, but most problems are caused by one of the handshake protocols, TLS-RSA. Here’s how that works:
The online shop server sends a letter box to the customer, in which the customer places a secret message and sends it back to the server. The webshop server opens the letter box, thus accessing the secret message, that is, the key.
The team performed a Bleichenbacher attack and gained access to the key. The IT experts fed errors into the secret message before putting it in the letter box and sending it to the server. The server, of course, expects that the incoming message has a specific form, so if it doesn’t, the error manager is launched. However, error management is more time-consuming than the server continuing key exchange as usual, and this time lag is what gave clues regarding the contents of the message.
The good news is, the new TLS version 1.3 is going to use a different protocol for key negotiation.
Chanwoo's Weekly Tech 