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1.3 KiB
1.3 KiB
Cryptpng
A proof of concept implementation of storing encrypted data inside of png metadata chunks.
Usage
# encrypt
cryptpng --image <name of the image> --in <input file> --out <output file>
# decrypt
cryptpng --decrypt --image <crypt image> --out <decrypted output file>
Technical Information
It should be possible to store data with a size up to ~ 4GB, but in reality most image viewers have
problems with chunks that are bigger than several Megabytes.
The data itself is stored in a png chunk
and encrypted via aes. The encryption chunk is stored right before the IDAT chunk that contains the
image data. The steps for encrypting are:
Encrypt
- Parse the png file and split it into chunks.
- Prompt for a password and use the sha512 32byte value.
- Create a base64 string out of the data.
- Encrypt the base64 string using aes and the provided hashed key.
- Store the data into the
crPtchunk. - Write the png header and chunks to the output file.
Decrypt
- Parse the png file and split it into chunks.
- Get the
crPtchunk. - Prompt for the password and create the sha512 32byte hash.
- Decrypt the data using aes and the provided hash key.
- Decode the base64 data.
- Write the data to the specified output file.