Secret Share app for iPhone and iPad

Secret Share is software that performs Shamirs secret sharing method.

The share and combine methods support the following four methods:

　(2, 2) 2 share 2 combine
　(2, 3) 3 share 2 combine
　(3, 3) 3 share 3 combine
　(3, 5) 5 share 3 combine

After sharing, each share piece is about 80 bytes larger than the source data.


It does not have an authentication function.

No error correction code is used.

The calculation is done using the Galois field.
The generated share piece is like a series of coefficients of Galois field of simultaneous equations.

It has something like random oracle.
Therefore, each attempt always produces a different piece of variance.


There is no limit on the size of files (data) that can be handled.

However, I think that
　about 1 MB
will be the realistic maximum size.

The reason is the time it takes to "combine".

The combine of secret sharing using "Shamias secret sharing scheme" takes a lot of time.

　1MB　　　　　about 1 minute or less
　about 15MB　about 5 to 15 minutes
　about 150MB　about 1 hour to 3 hours

It is like this. (I think its faster with a fast machine.)

However, it does not take so much time for share.
Usually, it takes about 1/10 of the time for combine.
However, combine takes much time.

Also, regardless of the number of variances of 3 and 5 share, 3 combine take
more than three times as long as 2 combine.
3 combine is simply 3 times longer than 2 combine.

On an old Windows XP machine, running (3, 5) 5 share 3 combine on a random
number of 158 MB takes such times:

　share　12 minutes 24 seconds
　combine　3 hours 10 minutes

Combining for 3 combine takes a considerable amount of time.