Gold'en Rant : Encryption makes your wireless life costly

You now, the mobile broadband lark is a bit of a con. Whereas users pay around £20.00 a month for squirting gigabytes of data across their landline broadband network, they really get shafted when it comes to 3G data services.

Unless they have a meal deal with their carrier. On 3, for example, I pay £15.00 a month for moving up to three gigabytes of data around. On my O2 contract, meanwhile, I pay £5.00 a month for a measly four megabytes of data.

But this is where it gets interesting. I've discovered O2's data packets appear to be transmitted when they are only partially filled at the packet switch interface.

Put simply - I can transmit a 200 kilobyte file from my O2 handset - using it as a modem for my laptop - and get billed for a megabyte.

The reason for this is the way O2 - and, I'll wager, the other cellular networks - treat encrypted data traffic.

Normally, eight bits goes into one byte when data is unencrypted, as the mobile data network can see the data coming in and analyse it for the best transmission.

This is why the Blackberry, which O2 pioneered in the early part of the decade, is so popular, as the Blackberry and the O2 network interact and compress data on the fly, meaning that a 10K email item gets compressed to around 2K before transmission.With encrypted data, this compression isn't possible, as the VPN software turns seven-bit ASCII files into multi-byte packets, owing to the data overheads involved with encryption.

O2's network then seems to split these multi-byte packets up and spread them over several packets - hence why a 200K file on my laptop turns into a megabyte as far as O2 is concerned.

I know this, as I've been logging my mobile data usage on my laptop, ever since getting seriously overcharged when roaming in France last summer.

Of course, there's no way to prove this is happening. Except on my 3 mobile broadband deal my laptop logs show 400 megabytes as being transmitted and received. On the Mythree log, however, I've used up 1.2 gigabytes of data.

Call me picky, but this seems a conspiracy. Itemised billing? Don't make me laugh...