Multi-signature wallet.

There are 5 Fift scripts and 1 script, written in FunC, for smart contract.

[new-wallet.fif] creates a BOC external message to create new wallet. Creates <n> private keys as well.
[new-order.fif] creates a BOC external message to the wallet to append new order for a transaction
[new-adder.fif] creates a BOC external message to the wallet to sign already existed sent order
[sign.fif] adds signature to a BOC external message (order or adder)
[info.fif] shows info of a BOC external message

External messages to smartcontract are divided into 3 groups:
[mode=0] first message of creation
[mode=1] creating new order (order request)
[mode=2] signing already sent orders (adder request)

Signing the order could be done in two ways:
1) One person creates a boc file of order request and asks others to sign it. When all signatures will be collected (or partially), boc file can be sent.
[!] While signing, seqno can be changed and request will not be accepted.

2) One person creates a boc file of order request and immidiatelly send it to the blockchain. Knowing the id of the order, he/she can ask others to push adder requests with their signatures to confirm the order.
[!] This method will use more gas.

~) As I wrote, order request could be sent even if not all signatures are collected. After that, adder request to add new signatures should be sent.

[tiny feature] Fift scripts are colourful!
You can check Colors.fif library, how I have done this.

Code is also available in GitHub: https://github.com/dkaraush/ton-multisig

plus:
Very fast (0.040G for a transfer with n=16, k=10)
accept_message() is called only after one signature was verified.

minus:
Not all features are implemented (merge signatures)