Add a random delay to broadcast scheduled transactions

[Technifocal]

Assuming I'm reading the code correctly, scheduled transactions are broadcast immediately after a new block is mined.

For example, imagine we had a transaction scheduled for block 3:

Block height	Time	Transaction broadcast/time
1	+0 minutes	False
2	+10 minutes	False
3	+20 minutes	True, at +20 minutes
4	+30 minutes	False

An attacker could assume that this transaction might have been scheduled. Compare this to:

Block height	Time	Transaction broadcast/time
1	+0 minutes	False
2	+10 minutes	False
3	+20 minutes	True, at +25 minutes
4	+30 minutes	False

Where an attacker could be sure the transaction was not scheduled as it came between two different blocks (and thus was not triggered by a block being mined).

Adding a random time after the target block (say, 0 seconds to 20 minutes) would prevent an attacker from determining that any transactions broadcast between two blocks were not broadcasted by Dojo's implementation of scheduled transactions.

[kenshin-samourai]

actually, there's already a random delay of a few seconds between the 2 events:

• delay for propagating the block between the miner and the full node hosted by dojo (through tor)
• delay for processing of the block by the tracker

That being said, the addition of a larger random delay (from a few seconds to a couple of minutes) might be a good idea.