http://www.newscientist.com/article.ns?id=dn6865&print=true
New Scientist
Simple snoop-proof email launched
16:04 11 January 2005
NewScientist.com news service
Will Knight
Software that aims to make encrypted email communications simple enough
for even computer novices to use was released on Tuesday.
Encryption is the science of securing communications against eavesdropping
by converting the content of a message into a code, or cipher, which can
only be unlocked using a secret "key". But modern cryptography often
involves using complex mathematical algorithms and convoluted key exchanges
to protect messages against skilled code-crackers.
Ciphire, developed by Ciphire Labs in Munich, Germany, uses a technique
called "public key cryptography" to sign and encrypt email messages. Once
loaded on to a computer hard drive the software performs all of the complex
tasks involved behind the scenes. Ciphire also works with almost any email
software client - like Microsoft Outlook, for example - without requiring
prior configuration.
"The real benefit is the ease of use," says Laird Brown, chief strategist
at Ciphire. "Everything is automated, so it's much like a virus scanner. It
just sits quietly in the background."
Brown told New Scientist the security of the system has also undergone
rigorous testing. "From a security perspective, we've taken it as far as we
can," he says. The program is being offered free for non-commercial use and
can be used by companies for a licence fee.
Virtual invisibility
Once installed on a PC, Ciphire runs in the background in conjunction with
an email client program. It intercepts email after the "send" button is
pressed but before the email leaves the computer, and intercepts incoming
email before it is formally received by the email program, making it
virtually invisible to the user.
The program automatically manages the creation of a set of public and
private cryptographic keys, simply prompting the user for a password from
which the keys are generated. The public key is sent to Ciphire's servers
and the private one is stored safely on the user's machine.
The two keys are mathematically linked in such a way that two independent
parties can communicate securely without first exchanging secret keys. A
private key can be combined with another person's public key to create an
encrypted message that can be deciphered using the corresponding public and
private pair.
Each time a message is sent Ciphire checks with its servers to see if the
recipient already has their own public key. If they do, the program uses
this to encrypt the message. At the other end of the exchange, the
recipient's version of the program should automatically retrieve the
sender's public key and perform the necessary decryption.
If the recipient does not have a key pair the program simply "signs" a
message - this key allows the recipient to confirm an email's authenticity
but does not protect it from eavesdroppers.
Unique signatures
The keys kept on Ciphire's servers are also utilised to generate coded
signatures unique to the content of each email message sent using the
system. If the content of a message is intercepted and altered somewhere
between being sent and received - this signature will not be the same,
alerting users to the tampering. Brown says this makes it virtually
impossible for anyone - including Ciphire itself - to change keys without
users becoming aware.
Ciphire had several independent cryptography experts audit the software and
made modifications based on their recommendations. Russ Housley, of US
company Vigil Security, who performed a study of the software, says that it
stood up to scrutiny.
"The security provided by Ciphire is very robust," he told New Scientist.
"In every situation, the designers have chosen the strongest possible
cryptographic algorithms and the longest possible key sizes."
Housley notes that Ciphire combines several encryption algorithms. This
means messages should remain secure even if a fundamental flaw should
emerge in one of the algorithms.
"This is like holding your pants up with both a belt and suspenders," he
says. "If one fails, your pants still stay up."
But Housley adds that the main advantage of the software is its simplicity.
"If it is difficult to use, then it will not be used," he says.
"Transparency is vital for acceptance by users."
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R. A. Hettinga