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Splitcoin is the safest way to encrypt your seed phrase. The Splitcoin app will never know or ask you for your seed phrase.


*The Splitcoin app is currently undergoing alpha testing.

It will soon be available for beta testing on both iOS and Android.

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“Most people are not able to back up their security keys; they will lose the device [...] They will not have the proper encryption for their backup; they will write it on a piece of paper, someone else will see it, and they will steal those funds.”

-Changpeng Zhao, CEO of Binance

A private key is like a password — a string of letters and numbers — that allows you to access and manage your crypto funds. The generation of these keys is made possible by the usage of cryptographic algorithms based on mathematical problems to produce a one-way function.


A seed phrase, also referred to as a “recovery phrase" is a 12 to 24 word code that is used as a backup access mechanism to a cryptocurrency wallet or associated private key. The seed phrase matches information stored inside the corresponding wallet that can unlock the private key needed to regain access.


Bitcoin Improvement Proposal, BIP-39, allows for the generation of a 12 to 24 word seed phrase from a dictionary of 2048 words. With the recovery phrase, users can regenerate a wallet that has become lost or damaged. Because they hold such access, BIP 39-enabled recovery phrases should be kept secret and stored securely. So how do we do this?

Keeping track of these seed phrases can be hard, especially for people who are not technologically savvy. Cryptocurrency is growing in popularity and more popularity means more wallets. Whether these are wallets for a single blockchain or a DeFi wallet to store multiple cryptocurrencies and NFTs, users need a simple way to back up their seed phrases. 

The Winklevosses came up with an elaborate system to store and secure their private keys. They cut up printouts of their private keys into pieces and then distributed them in envelopes to safe deposit boxes around the country, so if one envelope were stolen the thief would not have the entire key.

"How the Winklevoss Twins Found Vindication in a Bitcoin Fortune"

-Nathaniel Popper, New York Times, December 19, 2017

Splitcoin allows users to create a vault for their seed phrase by manually encrypting it using a unique auto-scrolling codebook. This codebook is unlocked by a unique vault key, which is split and stored across a set of NFC-enabled physical coins or QR codes. To retrieve their seed phrase, users simply scan their coins using the app and input their password. This opens the vault by allowing them to manually decrypt their seed phrase with the codebook. The app will never know or ask a user for their seed phrase.
How it works


app using NFC

AES-256-GCM encryption

Sleek, durable,

acrylic material 

Offline vault creation and vault opening processes

50 year data

retention period

Never needs


40mm diameter

2-8 coins

used per set


Never asks for your seed phrase


Your vault protects your seed phrase. Split and store your vault key across a set of Splitcoins, protected by AES-256-GCM encryption.


Use anywhere from 2-8 coins for a single set of Splitcoins. Using tools in the mobile application, you can easily make copies of your coins. It is a good idea to make backup sets!


NFC technology never requires charging. Simply scan your coins in the Splitcoin mobile application to read and write data. 


Create and open your vault using your two-way codebook, which is used to manually encrypt and decrypt your seed phrase. The mobile application will never know or ask for your seed phrase.


Acrylic coins act as durable and dedicated storage. Boasting a 50 year data retention period, they retain data much longer than the standard 10-20 years from SSD and HDD.


Data is air gapped and stored only on your coins. Optionally, you can also run the app on a secondary smartphone permanently in airplane mode to eliminate the risk of malware.

Create Vault

Secure. Distributed. Offline.

Splitcoin is an offline vault for your seed phrase that does not rely on any trusted third parties. Your encrypted seed phrase is your vault that protects your original seed phrase. This process will create your vault by showing you how to convert your original seed phrase into your encrypted seed phrase by hand. The key to your vault is stored securely across a set of physical, electronic coins or QR codes.


Open Vault

Secure. Distributed. Offline.

Splitcoin is an offline vault for your seed phrase that does not rely on any trusted third parties. Your encrypted seed phrase is your vault that protects your original seed phrase. This process will open your vault by showing you how to convert your encrypted seed phrase into your original seed phrase by hand. The key to your vault is stored securely across a set of physical, electronic coins or QR coins.


Splitcoin was designed to comply with these seed phrase storage best practices:

1. Never share your seed phrase with anyone.

2. Never store your seed phrase online.

3. Never enter your seed phrase into a device that is not a hardware wallet.


The three pillars of self-custody are described in what we call the Self-Custody Trilemma: Security, Distribution, and Connectivity. Splitcoin uses our proprietary SPLIT39 protocol, which allows the user to manually encrypt and decrypt their seed phrase using an auto scrolling codebook that is securely displayed in an iOS/Android mobile application. The app communicates with a set of data storage devices such as NFC tags or QR codes that are used to store and retrieve an encrypted vault key. These are called coins. The vault key securely stored on your coins unlocks your two-way codebook, which is protected by AES-256-GCM, a secure mode of authenticated encryption.


You will need all coins to open your vault. This is precisely why you should make backups of your coins. Found in the mobile application, Splitcoin Tools makes this easier than ever. Easily copy the data from one coin to another by using the Copy Splitcoin tool. This will read the data from the first coin by performing an NFC read and then write the data to the second coin by performing an NFC write. You can make as many sets of your coins as you like, and only need one full set to complete the vault opening process. Also, you can export your coins to QR codes or export your codebook to a PDF.


There is a level of trust that must be required when performing encryption using any piece of modern software. At some point, the plaintext must be typed in, processed by an encryption algorithm, and then the ciphertext is outputted. The same goes for decryption, where the ciphertext must be processed to output the plaintext. So how can a user be sure that the application is not malicious or that the developers of the software are not stealing their plaintext? Aside from trusting third party code reviews, how can the layman or everyday user get proof of this? Does this trust need to be reestablished with every software update? This highlights an important aspect of the Splitcoin manual encryption system. It utilizes modern day cryptography with military grade encryption and a strong key derivation function, combined with classical cryptography in the form of codebook encryption, to create the user experience of a pen and paper cipher.


This eliminates all risk of the seed phrase being leaked or stolen by malware, developers, or hackers, because the mobile application never sees the seed phrase.