> For the complete documentation index, see [llms.txt](https://learn.cypherock.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://learn.cypherock.com/getting-started/how-cypherock-generates-your-seed-phrase.md).

# How Cypherock generates your seed phrase?

Seed phrases, introduced by [BIP39](https://www.cypherock.com/blogs/post_what_is_bip39), are a recovery method that allows an individual to recover their assets in the case of loss of their crypto wallet, or any other case that would inhibit access to the wallet.

The very first step in creating a seed phrase is to generate entropy. Entropy in the case of wallets is a large, random binary number that is generated. Entropy and randomness are synonymous in the sense that the more entropy that exists, the less predictable the seed phrase in eventuality is going to be.

In the BIP39 standard, there are different lengths of seed phrases that can be generated, most commonly wallets generate 12/18/24 word seed phrases - each with their corresponding lengths of entropy in bits. For example, a 12-word seed phrase has 128 bits of entropy, whereas a 24-word seed phrase will have 256 bits of entropy.

In a 24-word seed phrase, there are 2^256 combinations of seed phrases possible. In comparison, there are 2^166 atoms in the universe. So, guessing a 24-word seed phrase is next to impossible.

{% tabs %}
{% tab title="Cypherock X1" %}
It is due to this magnitude that Cypherock will always generate a 24-word seed phrase.

## How entropy is generated in Cypherock X1

Cypherock X1 generates 256-bit entropy by utilizing True Random Number Generators (TRNG) which are [FIPS](https://csrc.nist.gov/glossary/term/federal_information_processing_standard) compliant.

The TRNG is built into the secure element of the device, as well as the MCU. For further clarification, Cypherock uses the following secure element and MCU respectively: ATECC608 and STM32L4.

The secure element, alongside the MCU each generate 32 bytes (256 bits) of entropy which are then combined using the XOR method. The XOR method is a fail-safe designed to ensure that even if either of the components, the MCU or the secure element has a backdoor in their random number generation, the seed phrase generated will still be random, hence avoiding the single point of failure here as well.

Normally, in other wallets, the output is stored in a single place - usually the secure element of the device. In Cypherock's case, once the entropy output of each of the chips is combined, Cypherock applies Shamir Secret Sharing at the entropy level to ensure that your seed phrase does not face a single point of failure.
{% endtab %}

{% tab title="Cypherock X0" %}
With Cypherock X0, you choose the length of your seed phrase when you create a new wallet: 12, 18 or 24 words, corresponding to 128, 192 or 256 bits of entropy.

## How entropy is generated in Cypherock X0

Cypherock X0 generates entropy using the hardware-based random number generator built into the EAL6+ certified secure element of the X0 Card.

The entropy is generated inside the secure element and is split into shards there, so the complete secret never leaves the X0 Card during wallet creation.

Normally, in other wallets, the output is stored in a single place - usually the secure element of the device. In Cypherock's case, Cypherock applies Shamir Secret Sharing at the entropy level to ensure that your seed phrase does not face a single point of failure.
{% endtab %}
{% endtabs %}

## Shamir's Secret Sharing

Shamir's Secret Sharing (SSS) is a secret sharing mechanism for distributing private information into cryptographic parts such that a certain threshold of parts is required to recreate the secret. This is done to avoid any one party involved in the sharing scheme compromising the secret.

Cypherock applies SSS at the entropy level during wallet creation.

{% tabs %}
{% tab title="Cypherock X1" %}
What this means is that the 256 bits of entropy are split into 5 cryptographic parts which are stored in the X1 Vault and the 4 X1 cards.

A threshold of 2/5 is applied, meaning that any two - X1 card and X1 Vault, or 2 X1 cards - can be used in conjunction to reveal the secret, which in this case would be the seed phrase.
{% endtab %}

{% tab title="Cypherock X0" %}
What this means is that the entropy is split into 5 shards inside the X0 Card, which are stored on the 4 X0 Cards and the user's smartphone.

A threshold of 2/5 is applied, meaning that any two - the smartphone and an X0 Card, or 2 X0 Cards - can be used in conjunction to reveal the secret, which in this case would be the seed phrase.
{% endtab %}
{% endtabs %}