Android Question SimplePGP eats bytes at the end of a file

[KapiteinOllie]

Hello, i experiencing some problems with encrypting/decrypting files with simplepgp.
Maybe i am doing something wrong or misunderstood the example.
But files with size 2Mb and bigger the simplepgp eats some bytes during encryption/decryption at the end of the file and makes the file corrupt.

    Dim password As String = RandomString(64)
    Dim pubkey As OutputStream = File.OpenOutput(File.DirData("temp"),"publickey.pem",False)
    Dim seckey As OutputStream = File.OpenOutput(File.DirData("temp"),"secretkey.pem",False)
    pgpkeys.Initialize("")
    pgpkeys.generateKeyPair2("pgp",password,1024,pubkey,seckey)
    
    Dim crypt As PGPMessageEncryptor
    crypt.Initialize("crypt")
    Dim data As InputStream = File.OpenInput(File.DirData("temp"),"file.mp4")
    Dim publickey As InputStream = File.OpenInput(File.DirData("temp"),"publickey.pem")
    Dim out_data As OutputStream = File.OpenOutput(File.DirData("temp"),"file.pgp",False)
    crypt.encrypt(publickey,"", data, out_data)
    
    Dim input_data As InputStream = File.OpenInput(File.DirData("temp"),"file.pgp")
    Dim secretkey As InputStream = File.OpenInput(File.DirData("temp"),"secretkey.pem")
    Dim decrypted_data As OutputStream = File.OpenOutput(File.DirData("temp"),"testfile.mp4",False)
    crypt.decrypt(password,secretkey,input_data,decrypted_data)

Can anybody confirm? Or is it just a me problem?

 

[emexes]

My first thought is that if it looks like the text is otherwise ok, just a bit shorter, that it's a character encoding issue.

Whereabouts can I download the B4A version of PGPMessageEncrypter from to give it a burl?

 

[DonManfred]

Whereabouts can I download the B4A version of PGPMessageEncrypter from to give it a burl?

Simple search for SimplePGP would have pointed you to the Librarythread ;-)

SimplePGP - Encrypt, Decrypt, Sign, Verify

This is a wrap around this Github-project. It wraps the Android Part of it using some additional jars from bouncycastle and spongycastle for the Encryption Provider A B4J Version is available here. I just did it out of curiosity :) Based on the Size of the Additional jars you need to download...

www.b4x.com

 

[emexes]

Simple search for SimplePGP would have pointed you to the Librarythread ;-)

True, but then I run into the question of: am I using the exact same version as the OP? And are we talking B4A or B4J? So simpler if they just point me to the one they're using, rather than me guess.

And I've just now discovered it seems the OP example code needs more than just the library to make it run.

 

[DonManfred]

And are we talking B4A or B4J?

As the thread is a B4A-Question i guess we are talking about B4A.

But you are right. The paths used looks like it were B4J

 

[emexes]

Simple search for SimplePGP would have pointed you to the Librarythread ;-)

Based on the Size of the Additional jars you need to download them here.

I am dropping out of the race. Collecting random stuff together to make the example compile is above my free-support paygrade.

If the OP is keen for an answer and provides a complete ready-to-compile example, I'll have another look.

 

[DonManfred]

I am dropping out of the race

The downloadlink you quoted is working here.

 

[emexes]

The downloadlink you quoted is working here.

Well, that's odd. Perhaps my internet connection is too slow. Or you're looking at a cached copy on your local computer?

 

[DonManfred]

Or you're looking at a cached copy on your local computer?

- I´m sure i haven´t downloaded it since 2018.
- My computer has a few restarts between
- I just clicked on the Link

and downloaded a fresh Copy

 

[emexes]

and downloaded a fresh Copy

For some reason it isn't downloading here. I think that is a sign from the gods above telling me to let it go, because dinner is on the table here.

If you've got the OP example running, was I anywhere in the ballpark with my guess about it being a character-encoding issue?

Although I've just realised that the example is for a binary video file, not for a text file, so... probably not.

But still, it'd be useful to confirm that the dropped bytes are from the end of the file, and that the rest of the file still matches what went in at the other end.

And then I'd try adding say 10k of recognizable junk at the end, and see what gets dropped, and if it's on a power-of-2 boundary.

Or maybe salt is getting added at the front but not properly desalted at the other end. Although... that doesn't sound like a bug that would exist very long in a widely-used library.

 

[emexes]

- I´m sure i haven´t downloaded it since 2018.
- My computer has a few restarts between

Only a few restarts in 7 years?

I'm impressed. I'm lucky if I get through 7 days without a restart.

 

[emexes]

But files with size 2Mb and bigger the simplepgp eats some bytes

Do (non-empty) files under 2 million bytes come out the other end being exactly the same size, and byte-for-byte identical eg

FC /B file.mp4 testfile.mp4

reports no differences found?

 

[DonManfred]

Only a few restarts in 7 years?

I was Joking

But Honestly: I´m not shutting down my PC usually/regularly.
I need a restart every few weeks though.
Mostly due to Windows-Updates wich requires a Restart

 

[KapiteinOllie]

Do (non-empty) files under 2 million bytes come out the other end being exactly the same size, and byte-for-byte identical eg

FC /B file.mp4 testfile.mp4

reports no differences found?

Just checked and also files of 4kb where simplepgp ate 1kb

 

[teddybear]

View attachment 162437

And here, it's the same.

Actually it's really there, because I can download it on my vmware

 

[emexes]

files of 4kb where simplepgp ate 1kb

Is that 4 kB test file innocuous enough that you can post it before and after it went through the PGP encryption-decryption wringer?

I'm interested to see if it's possible to work out whereabouts in the file the bytes were lost.

And also whether it might have been cut at an encryptionary-block-size-looking boundary.