Bitcoin Forum

Is it safe enough to keep the trezor/nano-S  seed words in two in two different secret locations with 12 words in each place?

Depends on those 2 places, and the type of paper and finishing you used...

I mean, you only need one copy to restore your wallet... So, it might be better to have one copy on a laminated paper in a bank's safe than writing those 12 words on some cheap paper and storing them with friends and relatives.

You'll also have to realise that if somebody else has access to your seed phrase, he/she could potentially rob you.

The 24 seedwords are split to two different safe boxes with 12 seedwords stored seperatelly...

Why do you need to store the seed secured? Answer this question and I guess you will find all the answer. Put them into one place only instead of 2. To keep it safe & secured, you must find a fire resistant place. Be sure that it’s secured enough. By the way, you can buy a suitcase which is fire resistance. I guess I have seen someone posting a few days ago here about this issue.

I've used ssss to create a 2 out of 3 setup for my own seed words... Put them on 3 usb sticks and i've stored 1 in a (locked) drawer in my office (i have my own, closed, room, inside a properly secured building), 1 is stored in my banksafe, 1 is stored at home.

It did require quite a setup... I wrote my seed phrase down, checked it, double checked it... Then booted my laptop using a live cd, disabled the wireless network interface (didn't plug in the wired network), then installed ssss, used it to encrypt my seed phrase, then stored 1/3 part on 3 usb sticks....

I did write down the procedure, and stored the live cd and the ssss source. After decrypting the seed, i verified it on my hw wallets, and afterwards i burned the paper containing the seed.

So, basically, if someone ever wants to rob me, he/she will have to break into a secured office, a bank and my home (well, 2 of those 3 places). Then he'll have to figure out that gibberish on the usb sticks he stole is an encrypted seed, then he'll have to figure out he needs to use ssss, then he'll have to guess my (long) passphrase.... If he does all that, i'll be robbed. While in the meantime, 2 out of 3 of the usb sticks will have to dissapear AND my hw wallet will need to be wiped before i can no longer access my funds

If you have all 24 words in one place and the paper is stolen, the thief steals your bitcoin.  
If you have 12 words in one place and the other 12 words in another place and someone steals one of the papers, the thief can't steal your bitcoin.  

In both cases, your coins are lost.

A solution is to create a multi-signature wallet. The other solution that comes to mind is to generate a SLIP39 seed.
The simplest solution is to have 2 copies from each of the 12 words. Keep the first 12 words in places A and B and the second 12 words in places C and D.

No. It will just make it more confusing for you to restore in 10-20 years, and you already have no room for error: one of the halves is gone, everything is lost.
If you really want to save the seed split in multiple locations it could be better to use something closer to a standard, like Shamir Backup (https://blog.trezor.io/shamir-backup-a-new-security-standard-3aa42a6ebb5f). But you'll need at least 3 location for that.

I urge you to take a look at this thread I started about a month ago > A. Antonopoulos’ Take on Seed Splitting and Bruteforcing (https://bitcointalk.org/index.php?topic=5356228.0).

Andreas explains why it's a bad idea to split your seed into multiple locations, how that reduces the entropy, and makes the seed exponentially easier to brute-force (maybe) sometimes in the future. There are also great posts by forum members and Andreas explains how Shamir's Secret Sharing Scheme makes it impossible for someone to gain an advantage (in terms of brute-forcing) if he discovered one part of the share. Less than the quorum, to be precise.   

I wouldn't recommend splitting your seed phrase up and I wouldn't recommend using Shamir's system either. With the former you are decreasing the security of your seed phrase. With the latter you are completely reliant on the particular implementation you used for recovery, and are completely trusting that that implementation contains no bugs or vulnerabilities. With both, you have a single point of failure in the device you used to generate the seed phrase or the device you will use to restore the seed phrase.

Whatever you are looking to achieve by splitting up your seed in either of these manners can be achieved more securely by using a multi-sig wallet.

That is terrible idea and you should NEVER do something like this splitting your seed words or mixing word order.
Better option is adding passphrase (that you keep separate from seed words) and using multisig option than you can store backups in multiple locations.
Whole point is to avoid single point of failure, and shamir backup is not providing that.

Placing your 24 Seed Phrase into 2 different location containing 12 word will result in a lot of issues.

1. Misplacing or forgetting location of 1 of the 12 word ~ automatically count as lost.
2. Rambling the words upon retrieving (i.e offline method)
3. Do not mix your seed phrase

I suggest, this one (https://github.com/jakob6102/seedcard). It requires a bit of work still you have access to your keys.