Turn your iPhone into a Digital Wallet

I just counted. I have 21 plastic cards in my wallet… credit cards, ID cards, membership cards, you name it. And there are four barcode tags dangling from my car keys.

Being a geek, I keep all the relevant numbers encrypted in my Palm Treo (using SplashID… I really hope they’re doing an iPhone version!), but rattling off a ten-digit number doesn’t do much good when the clerk at Barnes and Noble wants to see your card.

In preparing for the switch to an iPhone this weekend, I started thinking. Why not carry images of all those cards instead?

Here’s the video of the result:

(Sorry that it’s a little fuzzy. I didn’t want to recreate redacted versions of all my cards.)

Getting there is simple.

First, scan all your cards, front and back, on a flatbed scanner, at 200 dpi. (Actually, I didn’t do my credit cards, since I’m waiting for someone to come up with an encrypted version of this hack.) You’ll get a scanned page with multiple cards on the page.

Then, open the scan in Photoshop (or whatever image editor you like) and scale it so that each card takes about 470 pixels horizontally. You can do math, or you can just do trial-and-error. In my case, I found that scaling the image from 1700 pixels across to 1150 pixels worked well. Be sure to check the “Constrain Proportions” and “Resample Image” boxes.

Now select a rectangular selection tool and, using the pulldown menu, lock it to a fixed size of 480 x 320 pixels (the size of the iPhone screen).

Now play cookie-cutter… center the rectangular selection over each card image, copy, and paste each one into a new GIF file. Make sure to get the backs of cards where that information is relevant.

Save all these images into a folder. Launch iPhoto (on the Mac… I’m not sure how this works on Windows, but I’m sure you’ll figure it out) and import that folder. Rearrange the images to taste.

Now, in iTunes, sync that photo folder with your iPhone.

Here’s what you get:

Every card is displayed as a square icon. Most are recognizable, even at this small size.

Tap on the one you want, and you get a very legible version of each card on your iPhone screen:

And you can double-tap to zoom in, so you can read the fine print without your glasses!

In the zoomed view, I’ve been able to get a barcode scanner to recognize the image.

I hope this is useful to others out there. Now… someone wrap some encryption around this so that someone stealing my phone doesn’t wind up with all my ID numbers! 🙂


  1. Keith McGreggor says

    If you have a Fujitsu SnapScan, you can greatly simplify this process.

    1. set the SnapScan for JPG format, auto page size detection, dual side scanning.
    2. pull the paper guides in to roughly business card size.
    3. feed the cards in one by one.

    Very fast… you can capture business cards this way as well.

  2. Stephen,
    you continue to defy the time-space continuum. I have only 24 hours in my day. You must have at least 30!

  3. Bill McKinnon says

    Great idea! I’d be interested in how your transition goes — particularly the “total cost of conversion” (and what sorts of things that iPhone apps can’t quite do just yet). Some day it will be painful to have to give up my Treo.

  4. Interesting idea but a view from the UK is as follows.

    We are mandated to use cards that have chips storing cardholder data and then we enter a PIN to validate a transaction when paying. Signature is usually not allowed except when one is disabled etc and has a dispensation for such a bypass. Card fraud has fallen since they were introduced but for the following.

    Not using the chip-and-pin system makes all transactions ‘cardholder not present’ transactions which continue to grow as a category of card fraud. Businesses’ exposure is also greater in such cases.

    Besides I would like to know what your banks/ various card issuers think of this hack 🙂

  5. I’ve actually thought about this… and the use of mobile coupons as well. Instead of bringing a stack of coupons, launch your iphone and find coupons on the go and just have them scanned as you bring them up.

    Though, I do wonder if there are any long term negative effects from having a laser repeatedly hitting your iPhone screen to scan stuff.

  6. Anne Bubnic says

    You’re in luck. Splash ID just announced an IPHONE version yesterday!

    Your method is quite clever, but I hope you never lose that IPhone. Identity thieves would have a party.

    At least Splash ID has password protection!

  7. Didn’t think I’d see the value over other methods at first, but it is sometimes nice to have all of the details. Would be a great one if you ever lost your wallet and needed to know all your CC contact info to cancel cards

    One issue though would be bar code scans of “club cards”. I found a great hack on Lifehacker a while back, http://www.justoneclubcard.com. You enter in the store, the corresponding numbers and they spit out a printable card with all of your club card bar codes on it. You can even enter some that they don’t have the formula for on file, just takes some playing around.

  8. Susan Cartier Liebel says

    I’m just curious. Password protected or not…what happens when you iphone is stolen. No, they don’t have the physical cards to charge but your identity can be certainly compromised. Hacking is just not that hard, or worse, they steal it while you are using it and don’t need to worry about passwords.

    A friend had his stolen at knife point…makes me wonder, that’s all.

  9. digitalshaman says

    encryption only assures confidence in the communication. once decrypted, there is no "traceability" & to put it mildly your scheme is simple to hack. anyone with those cards can subtract your image from their own generated image – the difference should be the "value" being protected – hopefully unique to you but also unique to the issuers – you do not "own" the card; but, all of the other physical security features have been wiped, by you. I am not certain how liability is covered when you voluntarily rid yourself of security for convenience but what you have shown is akin to what simplistic counterfeiters do. There are techniques that I can provide that accomplish the same thing but they would be inappropriate here. Security versus convenience?expense versus value?

  10. Stephen Fleming says

    Nice to see some comments here!

    Good thoughts about encryption and security. Note that I'm using this for convenience, but not for anything that would really be a risk if stolen. I'm not sure what a criminal could do with my Barnes & Noble discount card, but I'm not terribly worried about it. 🙂

  11. digitalshaman says

    respectfully, you might be doing that but under the dmca & even certain contractual obligations (similar to those mentioned by the person from europe above) it may be unlawful … it raises a number of interesting issues – namely how do you balance security with convenience & piracy with privacy & theft of identity in general (your ID, the card ID & any transactional ID) – again, lots of discussion these days never takes into consideration copyright when it applies to items that you would think belong to you (like your cards) but the fact is that the risks and protection measures are the same in information theory … witness the recent MTA hacks by MIT for defcon … security by obscurity is bad but preventing healthy discussion and open debate is perhaps more detrimental …