Templates and User Guide for Manually Encrypting Cryptocurrency Seed Phrases Using an Alpha-Numeric Keypad and a 4-Digit Code

Background

In the field of cryptocurrency, securely storing private key seed phrases is critical to protecting one’s digital assets. One way in which phrases can be securely stored is by manually writing the phrase on paper (or in an electronic document). This specific method of storing phrases is vulnerable to unauthorized access. Unauthorized individuals can use the phrase, if discovered, to steal cryptocurrency funds. The following manual encryption method attempts to address this vulnerability using an alphanumeric keypad and a 4-digit code to obscure the seed phrase among decoy words.

Purpose

To securely store cryptocurrency seed phrases by manually encrypting them using an alphanumeric keypad and a 4-digit code.

Important Security Notices

This is not a private key/seed phrase generator. This method does not protect against brute force computer decryption. The following templates offer just 10,000 possible combinations, which equates to about 213. For a method to be secure against brute force attacks, a far greater number of combinations is required—typically 2128 or more. Please be mindful of this when using this method.

What You Need

  • A 12, 16, or 24-word cryptocurrency private key seed phrase (generated from your cryptocurrency wallet of choice).
  • The template(s) for the alphanumeric keypad provided.

    • It is recommended that users reference the BIP-39 word list and a word list randomizer to generate decoy words.

    Process Overview

    1. Select a 4-digit code (digits can be repeated up to 4 times).
    2. Divide your seed phrase into 4 equal parts.
    3. Map each part of the seed phrase to a specific section on the numeric keypad using your 4- digit code.
    4. Fill sections of the keypad that are not mapped to your seed phrase with decoy words.

    User Guide (Applies to 12, 16, 24 word seed phrases)

      Prerequisite:

      User already has a 12-word cryptocurrency private key seed phrase that was generated using a cryptocurrency private key seed phrase generator (e.g., a cryptocurrency wallet like Coinbase Wallet).

      Example Seed Phrase:

      apple banana cherry date eagle fish grape hat iron jam kite lime

      step 6 example

    1. Step 1: Determine Your 4-Digit Code

      User chooses their numeric 4-digit code. Digits can be repeated up to 4 times by using the 4 alphabetic subsections within a given digit. The code will be used to determine the organization of your seed phrase.

      Example Code: 5273

      step 6 sub 1 example

      Example Code (w/ Repeated Digits): 1223

      step 6 sub 1.2 example

    2. Step 2: Divide Your Seed Phrase

      Divide your 12-word seed phrase into 4 sequential parts, each containing 3 words in the original order of the seed phrase.

      Example Seed Phrase Parts:

      Section 1: apple banana cherry
      Section 2: date eagle fish
      Section 3: grape hat iron
      Section 4: jam kite lime

      step 6 sub 2 example

    3. Step 3: Assign Seed Phrase Parts to the Code

      Each of the 4 seed phrase parts corresponds with an alphanumeric section in your 4-digit keypad. Each digit has 4 alphabetically sequential sub-sections (A, B, C, D), allowing digits in the 4-digit code to be repeated up to 4 times. The first time that a digit is used in the 4-digit code populate subsection ‘A’; the second time that a digit is used in the 4-digit code populate subsection ‘B’; and, so on and so forth for sub-sections ‘C’ and ‘D’.

      Example with Code 5273:

      5A: apple banana cherry
      2A: date eagle fish
      7A: grape hat iron
      3A: jam kite lime

      step 6 sub 3 example

      Example with Code 1223 (Repeated Digits):

      1A: apple banana cherry
      2A: date eagle fish
      2B: grape hat iron
      3A: jam kite lime

      step 6 sub 3.2 example

    4. Step 4: Populate the Manual Encryption Template with Seed Phrase

      Populate each alphanumeric section of the manual encryption template with its corresponding seed phrase part.

      Example with Code 5273:

      5A: apple banana cherry
      2A: date eagle fish
      7A: grape hat iron
      3A: jam kite lime

      step 6 sub 4 example

      Example with Code 1223 (Repeated Digits):

      1A: apple banana cherry
      2A: date eagle fish
      2B: grape hat iron
      3A: jam kite lime

      step 6 sub 4.2 example

    5. Step 5: Populate the Manual Encryption Template with Decoy Words

      Populate each alphanumeric section of the manual encryption template that is not a part of the 4-digit code with decoy words (108 decoy words needed to fill in remaining sections). Decoy words should be selected from the BIP39 word list — the list from which all seed phrase words originate.

      Example Decoys:

      5B: water cloud bird
      2C: mountain river tree
      7B: stone sand leaf

    More Than 12 Words in Seed Phrase

    In addition to being used for 12-word seed phrases, this method can be applied to 16 and 24 word seed phrases simply by adding lines to the alphabetic subsections of the template.

    Example: Lines per alphabetic subsection needed for 12, 16, and 24 word seed phrases

    12 word: 3 lines, 4-digit code

    16 word: 4 lines, 4-digit code

    24 word: 6 lines, 4-digit code