can it be multiply offline transactions?
No, a key is either transferred via OtherCoin to a similar card or revealed to the user to be used in a Bitcoin transaction. It's either one or the other, as soon as the card gives you the secure part of the private key, it destroys it from its storage, so it can no longer be transferred via OtherCoin. It also destroys it as soon as it's transferred to someone else via OtherCoin.
So, to summarize, the security comes from the fact that all participants use the same hardware and software and that they cannot change the way the software works. They can't change the software to tell it to _not_ delete a private key after sending it or tell it to reveal its keys. It's a black box as far as the smartphone is concerned, you send some input to it and gives you some output, you don't control how it processes your input. What it does though is fairly public, it's described in the whitepaper and I can describe it further if needed.
Hello Drazvan,
I think what he might be asking here is whether or not or can do a series of off-chain transfers without having to put it back on-chain in betwen each transfer (ie: you transfer it to your friend as a loan and they transfer it to a shop for a purchase, the shop transfers it to some other customer as part of change, the customer transfers it to another shop, etc..).
So: Yes alex04210, you can do an infinite number of sequential off-chain transfers and every transfer is completely free! (Of course, the original transfer from the block-chain to the coin is on-chain and involves the standard bitcoin network transaction fees).
(By the way Drazvan, I've been meaning to contact all last week and discuss some things. Is it possible for you to private message me your email? )