I could briefly explain and put creation of new SecureSession 
architecture sketch on my medium stack. I have a few diagrams already 
which I will add, but none of this new SecureSession design. This is 
done so please check that page.

Reed Solomon encoding:
Using Reed-Solomon encoding for Forward Error Correction is used is 
satellite communications. Other lossy communications probably uses this 
or something similar. By interleaving RS encoded blocks, you quadruple 
the contiguous bytes that can be corrupted and still recovered. My use 
here will specify 4 interleaved blocks. So the encoding is really an RS 
encoding of 4 blocks and then interleaving them.

Note that QR Codes are using RS encoding.

RS encoding uses a GaloisField, or a finite field. This is a system of 
polynomials that are multiplied, divided, inversed and added to 
transform the data into code (as in coded data). The Galois Field is 
initialized with a primitive polynomial that sets the symbol size of 
data, symbol size of code and the number of errors that is still 
recoverable. Thus there are many different primitive polynomials as 
there are uses of RS encoding. Note that the symbol size tends to be a 
nibble. I use 3 different sized primitive polynomials, so I have 
different sized blocks depending on the size of the payload to be 
fragmented and encoded, in groups of 4 interleaved blocks.

The easiest RS encoding to look at has 9 data symbols, 15 code symbols 
and can handle 3 symbol errors. Considering that these 15 symbols/block 
will be interleaved with 3 other blocks, we are talking about 60 
symbols, or 30 bytes coded. This is 18 bytes of data. As they are 
interleaved with 3 errors per block permissible, that is 12 contiguous 
bytes can be corrupted and the msg recovered.

The interleaving takes the first byte from each of 4 blocks, then the 
second...

[byteA1, byteB1, byteC1, byteD1, byteA2, byteB2, ...]

I hope this helps! I'll add it to the project wiki.

Robert



On 12/05/2015 08:34 PM, Ben Coman wrote:
> This is interesting, "error correction through Reed Solomon encoding"
> but its not clear how its used.  Maybe a sketch of the architecture
> would be useful.
> cheers -ben
>
> On Fri, Dec 4, 2015 at 9:31 PM, Robert Withers
> <robert.w.withers at gmail.com> wrote:
>> Good morning,
>>
>> Here is a brief writeup of the SqueakElib project and its direction.
>>
>> https://github.com/SqueakCryptographySquad/Cryptography-Common/wiki/SqueakElib.
>>
>> All new squad members welcome.
>>
>> Regards,
>> Robert
>>