Error messages unlock internet payments protocol

ToshiroOC · Feb 21, 2003, 09:12 AM

A fundamental flaw in the technology used to secure online credit card transactions and other communications has been discovered.

Serge Vaudenay and his team, at the Swiss Federal Institute of Technology in Lausanne, found they could unlock an encrypted message by exploiting the error message scheme of the Secure Socket Layer (SSL) protocol.

The SSL protocol secures the link between a web browser or an email program and a web server. It is used by thousands of web sites to allow online credit card payments.

When an SSL message is sent to a server, the server's SSL program decrypts the message to check that it is the correct length and has been encrypted properly. If there is a problem, an error message will be sent back.

Vaudenay's team found that, by intercepting messages and modifying them in a particular way, they could cause the server to generate an error message that revealed part of the plain text message.

They demonstrated the attack in the lab by intercepting and modifying encrypted passwords sent to an email server. By generating 160 altered messages and analysing the error messages they prompted, they successfully worked out a password eight characters in length.

--By Will Knight, source: New Scientist

Article can be read here.

Feb 21, 2003, 09:12 AM	#1
ToshiroOC Unbiased. Join Date: Jun 2002 Posts: 4,812 Rep Power: 0	Error messages unlock internet payments protocol A fundamental flaw in the technology used to secure online credit card transactions and other communications has been discovered. Serge Vaudenay and his team, at the Swiss Federal Institute of Technology in Lausanne, found they could unlock an encrypted message by exploiting the error message scheme of the Secure Socket Layer (SSL) protocol. The SSL protocol secures the link between a web browser or an email program and a web server. It is used by thousands of web sites to allow online credit card payments. When an SSL message is sent to a server, the server's SSL program decrypts the message to check that it is the correct length and has been encrypted properly. If there is a problem, an error message will be sent back. Vaudenay's team found that, by intercepting messages and modifying them in a particular way, they could cause the server to generate an error message that revealed part of the plain text message. They demonstrated the attack in the lab by intercepting and modifying encrypted passwords sent to an email server. By generating 160 altered messages and analysing the error messages they prompted, they successfully worked out a password eight characters in length. --By Will Knight, source: New Scientist Article can be read here.