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Crypto Files

The following is a discussion of files used with cryptography, covering file names, encryption security, and file formats. It's not intended as a specification, but instead a survey of current methodologies. We are seeking discussion of this and other elements related to crypto-files, to create a community specification at some point in the future.

Table of Contents:

Currently Documented: Coldcard, Passport, Gordian Seed Tool

File Names

Coldcard: Backup Files

Coldcard Backup Files have file name format of:

backup.7z

Coldcard Backup Files uncompress to:

ckcc-backup.txt

Passport: Backup Files

Passport Backup Files have file name format of:

Master Fingerprint - "backup" - Backup #.7z

  • Master Fingerprint — The Hash 160 of the master public key.
  • Backup # — The incrementing number of the backup.

Example:

604b93f2-backup-1.7z

Passport Backup Files uncompress to: passport-backup.txt

Gordian Seed Tool: Data Files

Gordian Seed Tool outputs a variety of individual text and image data. They follow a consistent name scheme to allow easy sorting and lookup of data.

Seed Data Files

The general format for a seed file name is:

Seed Id - Seed Name - (optionally) Request or Response - Type - Format.filetype

  • Seed ID — The first 7 digits of the SHA256 digest of the seed.
  • Seed Name — Randomly created or user-selected name for object. Space separated.
  • Request or Response (optional) — Whether the file is a ur:crypto-request or ur:crypto-response.
  • Type — The type of object, in this case, "Seed" for a Seed or "SSKR" for the shares of a Seed.
  • Format — Output format, including "BIP39", "ByteWords", "Hex", "Identifier-Hex", "Lifehash", "Name" or "UR". Note that URs can be encoded as plain text (with a ".txt" suffix) or a QR code (with a ".jpg" suffix).

Examples:

ffa11a8-Yinmn Blue Acid Exam-Request-Seed-UR.png
ffa11a8-Yinmn Blue Acid Exam-Request-Seed-UR.txt
ffa11a8-Yinmn Blue Acid Exam-Response-Seed-UR.png
ffa11a8-Yinmn Blue Acid Exam-Response-Seed-UR.txt
ffa11a8-Yinmn Blue Acid Exam-Seed-BIP39.txt
ffa11a8-Yinmn Blue Acid Exam-Seed-ByteWords.txt
ffa11a8-Yinmn Blue Acid Exam-Seed-Hex.txt
ffa11a8-Yinmn Blue Acid Exam-Seed-Identifier-Hex.txt
ffa11a8-Yinmn Blue Acid Exam-Seed-Lifehash.png
ffa11a8-Yinmn Blue Acid Exam-Seed-Name.txt
ffa11a8-Yinmn Blue Acid Exam-Seed-UR.png
ffa11a8-Yinmn Blue Acid Exam-Seed-UR.txt
ffa11a8-Yinmn Blue Acid Exam-SSKR-ByteWords.txt
ffa11a8-Yinmn Blue Acid Exam-SSKR-UR.txt

SSKR Share Files

See above for SSKRs for a seed exported as a group. If SSKR shares are instead exported to individual files, per share, the format is:

Seed Id - [Group # _ Share #] - Checksum Words - Type - Format.filetype

  • Seed ID — The first 7 digits of the SHA256 digest of the seed.
  • Group # — The "group" plus the number of the share group (usually "group1").
  • Share # — Share number "of" total shares in group.
  • Checksum Words — Bytewords of the final four words in the share, which are checksums. Space separated.
  • Type — The type of object, in this case "SSKR" for the shares of a Seed.
  • Format — Output format, including ""ByteWords" or "UR". Note that URs can be encoded as plain text (with a ".txt" suffix) or a QR code (with a ".jpg" suffix.

Examples:

ffa11a8-[group1_1of3]-TRIP HAWK LUNG BELT-SSKR-ByteWords.txt
ffa11a8-[group1_1of3]-TRIP HAWK LUNG BELT-SSKR-UR.png
ffa11a8-[group1_1of3]-TRIP HAWK LUNG BELT-SSKR-UR.txt
ffa11a8-[group1_2of3]-CASH FIZZ MEMO PLAY-SSKR-ByteWords.txt
ffa11a8-[group1_2of3]-CASH FIZZ MEMO PLAY-SSKR-UR.png
ffa11a8-[group1_2of3]-CASH FIZZ MEMO PLAY-SSKR-UR.txt
ffa11a8-[group1_3of3]-ZERO CATS IRIS ROCK-SSKR-ByteWords.txt
ffa11a8-[group1_3of3]-ZERO CATS IRIS ROCK-SSKR-UR.png
ffa11a8-[group1_3of3]-ZERO CATS IRIS ROCK-SSKR-UR.txt

Key Data Files

The general format for a key file name is: Seed Id - Key ID - HDKey from Seed Name - (optionally) Request or Response - Type - [Derivation Path] - Format.filetype

  • Seed ID — The first 7 digits of the SHA256 digest of the seed.
  • Key ID — The first 7 digits of the SHA256 digest of the key.
  • HDKey from Seed Name — The prefix "HDKey from" prepended to randomly created or user-selected name for seed. Space separated.
  • Request or Response (optional) — Whether the file is a ur:crypto-request or ur:crypto-response.
  • Type — The type of object, in this case "PrivateHDKey" or "PublicHDKey".
  • Derivation Path — [Master Fingerprint (optionally) _ Path] _ (optionally) Fingerprint
    • Master Fingerprint — The Hash 160 of the master public key.
    • Path — The derivation path, using "h" for hardened. Underscore separated. Not used for Master Key.
    • Fingerprint — The Hash 160 of the derived key. Not used for Master Key.
  • Format — Output format, including "Base58", "Detail", "Identifier-Hex", "Lifehash", "Name", or "UR". Note that URs can be encoded as plain text (with a ".txt" suffix) or a QR code (with a ".jpg" suffix).

Examples of Master Keys:

ffa11a8-5db8946-HDKey from Yinmn Blue Puff-PrivateHDKey-[604b93f2]-Base58.txt
ffa11a8-5db8946-HDKey from Yinmn Blue Puff-PrivateHDKey-[604b93f2]-UR.txt
ffa11a8-bcab0a2-HDKey from Yinmn Blue Puff-PublicHDKey-[604b93f2]-Base58.txt
ffa11a8-bcab0a2-HDKey from Yinmn Blue Puff-PublicHDKey-[604b93f2]-Lifehash.png
ffa11a8-bcab0a2-HDKey from Yinmn Blue Puff-PublicHDKey-[604b93f2]-Name.txt
ffa11a8-bcab0a2-HDKey from Yinmn Blue Puff-PublicHDKey-[604b93f2]-UR.png
ffa11a8-bcab0a2-HDKey from Yinmn Blue Puff-PublicHDKey-[604b93f2]-UR.txt
ffa11a8-5db8946-HDKey from Yinmn Blue Puff-Request-PrivateHDKey-[604b93f2]-UR.txt

Examples of Other Key Derivations:

ffa11a8-607bf2a-HDKey from Yinmn Blue Puff-PublicHDKey-[604b93f2_48h_0h_0h_2h]_9ff1237f-Base58.txt
ffa11a8-607bf2a-HDKey from Yinmn Blue Puff-PublicHDKey-[604b93f2_48h_0h_0h_2h]_9ff1237f-Lifehash.png
ffa11a8-607bf2a-HDKey from Yinmn Blue Puff-PublicHDKey-[604b93f2_48h_0h_0h_2h]_9ff1237f-UR.txt
ffa11a8-607bf2a-HDKey from Yinmn Blue Puff-PublicHDKey-[604b93f2_48h_0h_0h_2h]_9ff1237f-UR.png
ffa11a8-607bf2a-HDKey from Yinmn Blue Puff-Request-PublicHDKey-[604b93f2_48h_0h_0h_2h]_9ff1237f-UR.txt
ffa11a8-607bf2a-HDKey from Yinmn Blue Puff-Response-PublicHDKey-[604b93f2_48h_0h_0h_2h]_9ff1237f-UR.txt
ffa11a8-8183ac1-HDKey from Yinmn Blue Puff-PrivateHDKey-[604b93f2_84h_0h_0h]_fac272cd-Base58.txt
ffa11a8-8183ac1-HDKey from Yinmn Blue Puff-PrivateHDKey-[604b93f2_84h_0h_0h]_fac272cd-Lifehash.png
ffa11a8-8183ac1-HDKey from Yinmn Blue Puff-PrivateHDKey-[604b93f2_84h_0h_0h]_fac272cd-UR.png
ffa11a8-db9b01e-HDKey from Yinmn Blue Puff-PublicHDKey-[604b93f2_84h_0h_0h]_fac272cd-Base58.txt
ffa11a8-db9b01e-HDKey from Yinmn Blue Puff-PublicHDKey-[604b93f2_84h_0h_0h]_fac272cd-UR.png
ffa11a8-db9b01e-HDKey from Yinmn Blue Puff-PublicHDKey-[604b93f2_84h_0h_0h]_fac272cd-UR.txt
ffa11a8-dc0c061-HDKey from Yinmn Blue Puff-PrivateHDKey-[604b93f2_48h_0h_0h_2h]_9ff1237f-Base58.txt
ffa11a8-dc0c061-HDKey from Yinmn Blue Puff-PrivateHDKey-[604b93f2_48h_0h_0h_2h]_9ff1237f-Lifehash.png

Address Data Files

The general format for an address file name is: Seed Id - Key ID - Address from Seed Name - Type - [Derivation Path] - (optionally)Format.filetype

  • Seed ID — The first 7 digits of the SHA256 digest of the seed.
  • Key ID — The first 7 digits of the SHA256 digest of the key.
  • Address from Seed Name — The prefix "Address from" prepended to randomly created or user-selected name for seed. Space separated.
  • Type — The type of object, in this case "Address".
  • Derivation Path — [Master Fingerprint (optionally) _ Path] _ (optionally) Fingerprint
    • Master Fingerprint — The Hash 160 of the master public key.
    • Path — The derivation path, using "h" for hardened. Underscore separated. Not used for Master Key.
    • Fingerprint — The Hash 160 of the derived key. Not used for Master Key.
  • Format — Output format, including "Lifehash" or "Name". If there is no Format, this is a plain address, either formatted in hex (as a .txt file) or in a QR (as a .png file).

Examples of Master Key Addresses:

ffa11a8-5db8946-Address from Yinmn Blue Puff-Address-[604b93f2]-Lifehash.png
ffa11a8-5db8946-Address from Yinmn Blue Puff-Address-[604b93f2]-Name.txt
ffa11a8-5db8946-Address from Yinmn Blue Puff-Address-[604b93f2].png
ffa11a8-5db8946-Address from Yinmn Blue Puff-Address-[604b93f2].txt

Examples of Other Addresses:

ffa11a8-8183ac1-Address from Yinmn Blue Puff-Address-[604b93f2_84h_0h_0h]_fac272cd.txt
ffa11a8-dc0c061-Address from Yinmn Blue Puff-Address-[604b93f2_48h_0h_0h_2h]_9ff1237f-Lifehash.png
ffa11a8-dc0c061-Address from Yinmn Blue Puff-Address-[604b93f2_48h_0h_0h_2h]_9ff1237f-Name.txt
ffa11a8-dc0c061-Address from Yinmn Blue Puff-Address-[604b93f2_48h_0h_0h_2h]_9ff1237f.txt

Output Data Files

Output data files contain a descriptor for a specific key derivation. They are derived from the master key. The general format for output file names is:

Seed Id - Key ID - HDKey from Seed Name - Type - [Master Fingprint _ Descriptor Type _ Account # _ Output Type _ Descriptor Checksum] - Format.filetype

  • Seed ID — The first 7 digits of the SHA256 digest of the seed.
  • Key ID — The first 7 digits of the SHA256 digest of the key.
  • HDKey from Seed Name — The prefix "HDKey from" prepended to randomly created or user-selected name for seed. Space separated.
  • Type — The type of object, in this case "Output".
  • Master Fingerprint — The Hash 160 of the master public key.
  • Account # — The number of the account.
  • Output Type — A textual descriptor of the derivation path, currently: "legacy", "legacymultisig", "nested", "nestedmultisig", "segwit", "segwitmultisig", or "taproot".
  • Descriptor Checksum — A checksum for the descriptor, as can also be retrieved by bitcoin-cli getdescriptorinfo.
  • Format — Output format, which is "UR". Formatted as textual UR (in a .txt file) or as a QR (in a .png file).

Examples:

ffa11a8-5db8946-HDKey from Yinmn Blue Puff-Output-[604b93f2_legacy_0_frs22d0f]-UR.txt
ffa11a8-5db8946-HDKey from Yinmn Blue Puff-Output-[604b93f2_legacymultisig_0_vwnxudyw]-UR.txt
ffa11a8-5db8946-HDKey from Yinmn Blue Puff-Output-[604b93f2_nested_0_cmyxclfa]-UR.txt
ffa11a8-5db8946-HDKey from Yinmn Blue Puff-Output-[604b93f2_nestedmultisig_0_ycs6cu6j]-UR.txt
ffa11a8-5db8946-HDKey from Yinmn Blue Puff-Output-[604b93f2_segwit_0_ncwysjuk]-UR.png
ffa11a8-5db8946-HDKey from Yinmn Blue Puff-Output-[604b93f2_segwit_0_ncwysjuk]-UR.txt
ffa11a8-5db8946-HDKey from Yinmn Blue Puff-Output-[604b93f2_segwitmultisig_0_wmsu2266]-UR.txt
ffa11a8-5db8946-HDKey from Yinmn Blue Puff-Output-[604b93f2_taproot_0_nay7kr6q]-UR.txt

Account Data Files

Account data files each contain several popular output descriptors. The general format for account file names is:

Seed Id - Key ID - HDKey from Seed Name - Type - Account # - Format.filetype

  • Seed ID — The first 7 digits of the SHA256 digest of the seed.
  • Key ID — The first 7 digits of the SHA256 digest of the key.
  • HDKey from Seed Name — The prefix "HDKey from" prepended to randomly created or user-selected name for seed. Space separated.
  • Type — The type of object, in this case "Account".
  • Account # — The number of the account.
  • Format — Output format, which is "UR". Formatted as textual UR (in a .txt file) or as a QR (in a .png file).

Examples:

ffa11a8-5db8946-HDKey from Yinmn Blue Puff-Account-0-UR.txt
ffa11a8-5db8946-HDKey from Yinmn Blue Puff-Account-1-UR.txt

Encryption

Coldcard: Backup Files

Coldcard backup files are 7zipped and encrypted with twelve space-separated BIP-39 words.

Passport: Backup Files

Passport backup files are 7zipped and encrypted with six space-separated Bytewords.

Gordian Seed Tool: Data Files

Gordian Seed Tool files are not encrypted.

Contents

Coldcard: Backup Files

Coldcard backup files contain a variety of key-value information in a plain text format:

# Coldcard backup file! DO NOT CHANGE.

# Private key details: Bitcoin
mnemonic = "fly mule excess resource treat plunge nose soda reflect adult ramp planet"
chain = "BTC"
xprv = "xprv9s21ZrQH143K4Mnjc7E8rpSMf8JB1XWmojYf7Ndk6zcNSbUYBsvTqJcdzTok1XwYcgytn5CRxtwhHu93NNXNQwGUbBqL3AHHZZrtKpEvmww"
xpub = "xpub661MyMwAqRbcGqsCi8m9DxP6DA8fQzEdAxUFum3MfL9MKPogjREiP6w7qjaeHuDUGuVmgCFf5iMntcyVoHsEFMKoxo7UxMpmafjeQofQezj"
raw_secret = "8059f2293a5bce7d4de59e71b4207ac5d2"
long_secret = "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"

# Firmware version (informational)
fw_date = "2020-08-06"
fw_version = "3.1.9"
fw_timestamp = "200806172219"
serial = "205C33613252"

# User preferences
setting.chain = "BTC"
setting.tested = true
setting.terms_ok = 1
setting.words = true

# EOF

Passport: Backup Files

Passport backup files contain a variety of key-value information in a plain text format:

# Passport backup file! DO NOT CHANGE.

# Private Key Details: Bitcoin
mnemonic = "fly mule excess resource treat plunge nose soda reflect adult ramp planet"
chain = "BTC"
xfp = "604B93F2"
xprv = "xprv9s21ZrQH143K4Mnjc7E8rpSMf8JB1XWmojYf7Ndk6zcNSbUYBsvTqJcdzTok1XwYcgytn5CRxtwhHu93NNXNQwGUbBqL3AHHZZrtKpEvmww"
xpub = "xpub661MyMwAqRbcGqsCi8m9DxP6DA8fQzEdAxUFum3MfL9MKPogjREiP6w7qjaeHuDUGuVmgCFf5iMntcyVoHsEFMKoxo7UxMpmafjeQofQezj"
raw_secret = "8059f2293a5bce7d4de59e71b4207ac5d2"

# Firmware Version (informational):
fw_version = "1.0.8"
fw_date = "December 29, 2021"

# User Preferences:
setting.backup_num = 4
setting.backup_quiz = true
setting.chain = "BTC"
setting.next_addrs = {"0/None": 0, "0/7": 1}
setting.terms_ok = 1
setting.validated_ok = 1
setting.wallet_prog = {"deriv_path": "m/84'/0'/0'", "export_mode": "qr", "acct_info": [{"acct": 0, "deriv": "m/84'/0'/0'", "fmt": 7}], "sig_type": "single-sig", "exported": true, "addr_type": 7, "verified": false, "multisig_id": null, "acct_num": 0, "next_addr": 0, "sw_wallet": "BlueWallet"}
setting.words = true

# EOF

Gordian Seed Tool: Data Files

Gordian Seed Tool contents are simple datums with data Type and Format specified in the filename. UR format content is in addition self-identifying, whether saved as a ur: text string or a QR code.