價格：免費
更新日期：2017-03-28
檔案大小：5.5 MB
目前版本：1.01
版本需求：需要 iOS 6.0 或以上版本。與 iPhone、iPad 及 iPod touch 相容。
支援語言：英語
Lgit is a unique app that will take a photo and prove that you did so legitimately without any extra modifications.
Why you may want to use it ? Here's a couple of reasons :
- Do you want to prove to someone that a photo is not photoshopped ? Just take a picture with Lgit and email it to them !
- Do you want to buy a second-hand product and can't tell if a product's photo is real and recent ? Tell them to use Lgit and send you the photo by email, then verify it !
- Do you want to make sure a photo of someone is recent and real ? Tell them to use Lgit, if they can generate new pictures with correct hashes they're real or recent !
- Do you run a news outlet and you can't trust your sources on wether they're providing authentic pictures of unreleased gadgets ? Make them use Lgit and then verify the photo !
- Do you want to prove to someone you are in a unique location, be it an exotic country, or on top of a tall building ? Use Lgit to take the picture, then tell them to verify it. If the hashes match, it's Legit !
- Do you need to provide or request proof that you've visited an address, met or talked to a person, delivered a product or performed a task ? Use Lgit and email the photos for verification. If the hashes match, it's Legit !
How to use it ?
Just use Lgit to take the photos ! This will guarantee that the picture was done with the app as there is no other app
that locks the pixels of the image through cryptography. If even one pixel is modified, altered, or if the image is resized
or cropped, the verification process will fail !
Let's imagine a use case scenario :
You want to sell an iPad to someone, he asks if the serial number is real so he knows you're sending an iPad 4 and not an iPad 2, right ? You make a picture with your iPhone, save it on your computer and decide to send it to the guy for verification the next day. But that night one of your friends comes by and edits the photo to make it brighter without you knowing it and saves over the original. The next day when you send the photo to the buyer for verification, he receives the photo in the mail, loads it on his iPhone, runs the app, verifies the photo and then sees that the expected hash is incorrect. He then basically knows that the photo has been tempered with. Now let's say he asks another photo cause you say the thing is legit. You take another photo which has a different hash and send it to him immediately, he will then receive it, verify it and the expected hash will match, letting him know the photo is now legit.
How does it work ?
This is kind of technical but here goes : there's an algorithm that is run based on ALL the pixels from an image. Each pixel's
intensity is run through a cryptographic function (SHA256). This ensures that the hash being outputted is unique for each
image and that even if a pixel color changes slightly, the hash will be completely different. On top of that the image hash is mixed in with a private key in order to guarantee that the hash comes from this app and ONLY this app !
Can someone fake the hash ?
Absolutely not. The input of the hash function is the image's pixels but is also mixed with a private key to make sure that the hash
generated comes from exactly this app and ONLY this app !
The hash doesn't match, what happened ?
File conversions, like converting a PNG to a JPG will break the hash even if you think the image is the same ! Only loseless image
formats that keep the original image intact are ok to use (like PNG or BMP).
Additionally when you share through facebook or twitter those services will automatically convert as you will not be able to verify them as authentic afterwards. This is a feature, not a bug !
支援平台：iPhone, iPad