cns007.txt

 



CRYPTONOTE STANDARD 007                                Antonio M. Juarez
Category: Main Track                                        Oscar Norton
                                                               Neocortex
                                                           Albert Werner
                                                              CryptoNote
                                                           November 2012


                     CryptoNote Keys and Addresses


Abstract

   This document is part of the CryptoNote Standards describing a peer-
   to-peer anonymous payment system. It defines various types of user
   keys used in CryptoNote and the way the addresses are encoded into
   alphanumeric strings.


Copyright and License Notice

   Copyright (c) 2012 CryptoNote. This document is available under the
   Creative Commons Attribution 3.0 License (international). To view a
   copy of the license visit http://creativecommons.org/licenses/by/3.0/


Table of Contents

   1. Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . .  2
   3. Address and Keys  . . . . . . . . . . . . . . . . . . . . . . .  2
   4. Address Serialization . . . . . . . . . . . . . . . . . . . . .  3
   5. CryptoNote Base58 . . . . . . . . . . . . . . . . . . . . . . .  4
   6. References  . . . . . . . . . . . . . . . . . . . . . . . . . .  5














 


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1. Introduction

   CryptoNote Standards can refer to the term "keys" in two cases:

      1) One-time private and public keys used in transactions.
      txout_to_key is the basic transaction type in CryptoNote. See
      [CNS004] for details.

      2) User's permanent keys stored in personal CryptoNote wallets.
      They are used for checking incoming transaction and deriving one-
      time private keys for ring signatures.

   Each user has two pairs of (private, public) permanent keys by
   default. The public parts of the keys are represented as user
   address.


2. Definitions

   public key: a datum used to identify a peer for the purpose of
   digital signature verification

   secret key: data known to a peer only, which enables him to create
   digital signatures under his identity


3. Address and Keys

   In order to send money, one needs two public keys corresponding to
   the two secret keys the receiver possesses. These keys allow him to
   send unlinkable payments (see [CNS002] and [CNS006] for details).


                           +----------------+
                           |                |
                           |  Public key A  |
                           |                |
                           +----------------+                
                           |                |
                           |  Public key B  |
                           |                |
                           +----------------+

            Figure 3a: Full address for unlinkable payments


   When serialized to a string, these keys become a human-friendly
   CryptoNote address.
 


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   Spend key is a pair of secret keys corresponding to the public keys
   in a CryptoNote address. Spend key is required to sign transactions. 

                           +-----------------+
                           |                 |
                           |   Secret key a  |
                           |                 |
                           +-----------------+
                           |                 |
                           |   Secret key b  |
                           |                 |
                           +-----------------+

                          Figure 3b: Spend key


   View key consists of one secret key corresponding to a public key in
   a CryptoNote address and one public key from the same address. View
   key allows its holder to identify incoming transactions,
   circumventing unlinkability. Said key does not allow the holder to
   spend any funds.

                           +----------------+
                           |                |
                           |  Secret key a  |
                           |                |
                           +----------------+
                           |                |
                           |  Public key B  |
                           |                |
                           +----------------+

                          Figure 3c: View key 
                                    

   CryptoNote keys are Ed25519 keys encoded into 32 bytes. See
   [ED25519].


4. Address Serialization

   CryptoNote addresses are serialized to strings using CryptoNote
   Base58 encoding scheme. The data encoded consists of three parts:

      - public address prefix (used to distinguish the addresses of 
        different currencies),

      - a pair of public keys,
 


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      - checksum.

   The pseudo-code below defines the process of generating an address:

      Checksum = H(Varint(Prefix) || A || B)[0..3]
      SerializedString = Base58(Prefix || A || B || Checksum)

   H here is the Keccak function that is used in CryptoNote, and ||
   denotes concatenation. For varint (variable-length encoding of
   integers) description see section 3 of [CNS003].


                                         Keccak
                      +-----------------------------------+
                      |                                   |
                      |                                   V
   +---------+-------------+-------------+   +----------+--------------+
   | Public  |             |             |   | Checksum |              |
   | address |      A      |      B      |   |  (first  |    Unused    |
   | prefix  |             |             |   | 4 bytes) |              |
   +---------+-------------+-------------+   +----------+--------------+

   +----------------------------------------------------+
                              |
                              | Base58
                              V
                   +--------------------+
                   | CryptoNote Address |
                   +--------------------+

               Figure 4: Address serialization algorithm


5. CryptoNote Base58

   CryptoNote Base58 is a binary-to-text encoding scheme used to
   represent arbitrary binary data as a sequence of alphanumeric
   characters.

   CryptoNote Base58 uses the following alphabet:

      123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz

   The input is split into 8-byte blocks. The last block may be smaller
   than 8 bytes. Each block is interpreted as a big-endian integer,
   converted into base 58 (again, big-endian), and encoded using the
   alphabet shown above. The number of base-58 digits used to encode a
   block is the smallest number of digits sufficient to encode every
 


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   block of the same size. For example, 8-byte blocks are encoded using
   11 characters.


6. References

   [CNS002] "CryptoNote Signatures", CryptoNote Standard 002, May 2012.

   [CNS003] "CryptoNote Blockchain", CryptoNote Standard 003, September
   2012.

   [CNS004] "CryptoNote Transactions", CryptoNote Standard 004,
   September 2012.

   [CNS006] "CryptoNote One-Time Keys", CryptoNote Standard 006,
   November 2012.

   [ED25519] Bernstein, D. J., Duif, N., Lange, T., Schwabe, P., and B.-
   Y. Yang, "High-speed high-security signatures", 2011,
   http://ed25519.cr.yp.to/ed25519-20110926.pdf.































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