IOTA tutorial 23: Masked Authenticated Messaging Demo Store File

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This is part 23 of the IOTA tutorial.

In this video series different topics will be explained which will help you to understand IOTA.
It is recommended to watch each video sequentially as I may refer to certain IOTA topics explained earlier.

The main objective of this video is to demonstrate a Masked Authenticated Messaging use case.

During making of this tutorial, I encountered a bug in the mam.web.js library (commit: feb 5, 2018; commit hash: a365e8f).
The bug is in decode function in the Rust code which can only handle messages up to a certain size:

Please note: This library is work in progress.
A workaround this bug is to break up messages into chunks and upload a stream of MAM messages.
If you have watched IOTA tutorial 19 and 22 and you are using my demo web applications be aware of this bug!

Two web applications are created to demonstrate storing files on the Tangle using Masked Authenticated Messaging.
Demo 1:
The uploaded file is not broken up in chunks.
Due to the bug this web application only works for small files, 5 Kbytes or less, in any channel mode and security level.

Demo 2:
The uploaded file is broken up in chunks.
This web application works for any uploaded file size, channel mode and security level.
Both web applications are created for educational purpose and can store any file types (text files or binary files) on the Tangle.

Please note: In this video a file is also considered to be a message.
When using MAM, try to avoid breaking up a message in chunks.
For each chunk a masked payload and therefor a transaction bundle is created.
Creating a masked payload creates overhead: index, message length, nonce, signature, number of siblings and siblings.

Can I use MAM to store a large message on the Tangle, for example a 1 MB pdf file?

Yes, you can, but do you want to do this?

Lets assume the bug is fixed and you do not have to break up the 1 MB pdf file in chunks.
This file is stored on the Tangle by creating a transaction bundle containing multiple transaction objects.
Each signatureMessageFragment field of these transaction objects contains part of the file.
For each transaction object a Proof of Work needs to be done.

A 1 MB message equals ~1,764,208 trytes (not taking into account other masked payload overhead).
The transaction bundle consists of 1764208 / 2187 = ~807 transaction objects.
The PoW takes ~19 sec per transaction object.
I have done some non scientific measurements and came to this number.
Please do your own measurements!

Time spent for the PoW = 807 x 19 sec = ~4.25 hours
To store a 1MB message on the Tangle takes ~4.25 hours

The main purpose of this calculation is to inform you that storing a large message size on the Tangle takes a lot of time.

After a snapshot all stored files are deleted from the Tangle.
The stored files are still available, if the subscriber is connected to a permanode.

Lets assume a software update (few kBytes in size) is stored on the Tangle.
To simulate a software update, create a file: mobilefish_change_color.txt.
This file must contain a single line containing a colour code, for example #ff0000
Use one of the demo web applications to upload the mobilefish_change_color.txt to the Tangle.
Use the same web application to retrieve the uploaded file.
It will change the web application background colour simulating a software update.

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The presentation used in this video tutorial can be found at:

#mobilefish #howto #iota

Post Author: CoinCryptoNews