Carrying a seed across a border

A border is the one place where a stranger with authority can open your bags, read your papers and, within limits, look through your phone. It is also the reason this site exists: a seed phrase written as words will not survive that, and a seed phrase written as numbers from a public cipher looks like a receipt. This page is about the trip itself, not the law. The border searches page covers what can be compelled and what can't.

What gets searched

U.S. Customs and Border Protection publishes its device search counts. In fiscal year 2025 it searched the electronic devices of 55,318 travellers out of more than 419 million it processed, under 0.01 percent. Most of those were "basic" searches, an officer looking through the device by hand; about 4,400 were "advanced", with the device connected to equipment that copies it. CBP's own policy limits a search to what is on the device, not what is in the cloud, and officers are instructed to put the device in airplane mode first.

Two things follow. The odds of a device search on any one trip are low. And when it happens, it is a search of the device's contents, by a person or by a copier. A seed phrase in a notes app, a photo of a metal plate, a stego image that a copier will preserve bit for bit: all of these are on the device.

Bags and papers get looked at more often than phones and more casually. An officer opening a bag is looking for goods, cash and contraband. A receipt is none of those.

What to carry

The numbers, on paper, disguised, with a passphrase that isn't with them.

1. Before the trip, encode the seed with a cipher from the vault and write the twelve or twenty-four numbers into something that belongs in your luggage. The disguise page works five forms. A packing list with weights. A receipt. A page of a travel journal with prices and times.
2. Remember the cipher by its name (a colour, an adjective, an animal, with a date). Do not carry the cipher. It is on this site, on the mirrors, and in the torrents, and you can fetch it at the other end.
3. Carry the passphrase in your head, or leave it with the person you trust at home, or in a second place you can reach after arrival. Never on the same paper, never on the same device.
4. Leave the hardware wallet at home, or carry one that holds nothing. A hardware wallet in a bag is a declaration that a seed exists.
5. Leave the seed words at home, in your real backups, where they belong.

The public example phrase on this site, pizza educate fat kiss domain venue …, encoded with the Red Crowded Ape cipher of 2 January 1770, becomes a handful of four-digit numbers. On the home page they are a hardware-store receipt. The receipt crosses a border as a receipt.

We will never ask for a seed word or a passphrase, and you should never type one into this site or any tool it links to.

What to leave

The methods on the earlier pages, ranked for travel:

• A seed on a phone in any form is the weakest. Notes, photos, password managers, and stego images all sit on the device that gets searched or copied. An advanced search copies the stego image intact, and a later search of the copy has all the time in the world.
• A stego image is the second weakest, for the reason above and for a second one: a phone that syncs photos has already uploaded the image to a cloud library that may have re-encoded it, and the copy on the phone may be the re-encoded one. You find out at the destination.
• A word puzzle travels well on paper and badly if it is obviously a puzzle about money. A crossword in a crossword book is fine.
• A null-cipher letter travels well. People carry letters.
• A metal plate is the strongest at home and the worst in a bag. It reads as a seed backup to anyone who has seen one, and it sets off the metal detector.
• A memorised seed, words or numbers, travels perfectly and fails on arrival if you have the memory of a person who just flew twelve hours. Memory is a second copy, not the only one.

At the other end

Fetch the cipher. Open the decode file. Read the words back. Enter them and the passphrase into a wallet you trust, on a device you trust. If the destination is somewhere you don't trust the devices, the numbers stay numbers until you are somewhere you do.

Then destroy the paper, or keep it, as you prefer: the numbers alone open nothing while the passphrase is elsewhere, and the receipt was never evidence of anything.

Where this breaks

It breaks if you carry the cipher, because then the paper and the key are in the same bag. It breaks if you carry the passphrase written down. It breaks if the disguise is bad: twelve numbers on a sticky note are a list, and a list is a question. And it breaks if the officer already knows who you are and what you own, which is the second person again, and no disguise answers that person. The passphrase does.

Sources