Yahoo mail blocked me from sending a program I wrote, what can I do?

[sysprog]

I was actually thinking first class mail. The point is to get some code to the guy's grandson. And we're talking about jpeg steganography?

USPS small package service is a 'species' of first-class mail $--$
from https://www.usps.com/ship/mail-shipping-services.htm:

First-Class Mail® is an affordable mail service for standard-sized, single-piece envelopes weighing up to 3.5 oz and large envelopes and small packages weighing up to 13 oz with delivery in 3 business days or less.​

​

(emphasis added)​

The method is not steganography; it's simply XOR masking -- if a .jpg file is used as the mask, it's sent without alteration. The .exe file is XORed against the mask file (of the same or greater length), and the resulting data file is sent along with the mask. Then at the receiving end, the data file is XORed against the mask file, and the result is the .exe file.

The method is the same as that used for a one-time pad cipher, except that it sends the mask file with the data file instead of by separate transmission, the mask doesn't have to be random, and it can be used more than once $-$ the goal here isn't imperviousness to cryptanalysis; it's getting past a filter by eliminating the characteristic patterns that the filter searches for.

For real one-time pad security, you could use two DVDs filled with identical random data, send one to your correspondent, and then send XOR-masked data files, each with an offset number for how far into the DVD was up next for use as a mask. Then a script could copy bytes from the DVD, beginning at the current offset, and running the length of the data file. The new offset for the next file to be sent, in either direction, would be the offset just used plus the length of the data file just sent. With a standard 4.6GB DVD, that would allow for 460 program or other files of 10MB length each, or a lot of smaller files.

 

[jedishrfu]

Perhaps we should be looking at google drive file sharing now. We wouldn't want to hide the data from the feds (who likely know about XOR masking already).

 

[sysprog]

Perhaps we should be looking at google drive file sharing now. We wouldn't want to hide the data from the feds (who likely know about XOR masking already).

The method described in my post #28 here is not secure against government cryptanalysis, and there are difficulties in practical implemention of genuine one-time pad cryptography, not the least of which is rapid and reliable generation of 'truly random' data.

 

[Vanadium 50]

The method described in my post #28 here is not secure against government cryptanalysis

It's OK. He's sending something to his grandson. It doesn't need to be secure against major world governments.

 

[berkeman]

I got an e-mail from a foreign government official (I'm not at liberty to say which country) requesting that I temporarily lock this thread for Moderation...

 

[PeterDonis]

I am sure people send .exe by email, or else how can programmers work at home!

You must be joking. The usual way of sharing source code is by distributed version control systems such as git. The usual way of sharing executables is by providing them via properly secured download links or packages shipped with operating systems. Nobody shares code or executables by email.

 

[berkeman]

You must be joking. The usual way of sharing source code is by distributed version control systems such as git. The usual way of sharing executables is by providing them via properly secured download links or packages shipped with operating systems. Nobody shares code or executables by email.

Well, to be fair. We used to do this all the time 5-10+ years ago in my company. But with more strict (and justified) security measures in place, we no longer can do that, so we use OneDrive or our internal servers, etc. to do it as I've already posted in this thread.

 

[jedishrfu]

As @berkeman has said in a prior post, it’s time to close off this thread. We have explored the breadth and depth of the problem and find that once we have over engineered our answers. We have given the OP multiple avenues to try out while his grandson is anxiously awaiting its arrival by email or snail mail.

As @PeterDonis has intimated professionals use professional methods while the rest of us use whatever works. Oh how times have changed in the software world from simple file backups to SCCS, RCS, CVS, SVN, and now GIT. For my own projects, I tend to use Google Drive for large zip files and email for scripts. I’ve not had a need to develop exe files in a long time But would likely use the drive approach to bypass the email block. The drive approach allows me to change the file while keeping the email reference intact.

Thank you all for contributing here and without further ado will close this thread forever.