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Optionally restrict a token to a set of addresses #287

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merged 5 commits into from
Nov 7, 2014
Merged

Optionally restrict a token to a set of addresses #287

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f1af0a7
First cut at restricting a token to a list of addresses
dacoinminster Nov 5, 2014
027f3bf
Merge branch 'master' of https://github.com/mastercoin-MSC/spec
dacoinminster Nov 5, 2014
e466a23
Changes after talking to Zathras about this PR
dacoinminster Nov 5, 2014
e6c8c68
Actually need 21 bytes, not 20
dacoinminster Nov 5, 2014
d9d94a7
Reverting whitespace-only changes
dacoinminster Nov 6, 2014
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52 changes: 48 additions & 4 deletions README.md
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Expand Up @@ -245,6 +245,11 @@ This section defines the fields that are used to construct transaction messages.
+ Size: 32-bit unsigned integer, 4 bytes
+ Valid values: 0 to 4,294,967,295

### Field: Bitcoin Address
+ Description: the 21 bytes needed to uniquely identify a bitcoin address (checksum removed)
+ Size: 21 bytes, binary data
+ Valid values: any 21 bytes (version + output of RIPEMD-160 hash step of creating a bitcoin address)
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The language is a bit flawed: a public key hash has a length 20 bytes and used in most standard transaction. Base58 encoding, checksums, versions and so on are "on top". This sounds as if you start from 16UwLL9Risc3QfPqBUvKofHmBQ7wMtjvM to get to 00010966776006953d5567439e5e39f86a0d273bee, but it's actually the other way around. What is "hash step of creating a bitcoin address"?

This helps and is a good overview of the steps involved:
https://en.bitcoin.it/wiki/Technical_background_of_Bitcoin_addresses

Edit: by the way: gratulations for spotting the need of a version byte. I overlooked this. :)


### Field: Number of coins
+ Description: Specifies the number of coins or tokens affected by the transaction this field appears in, as follows:
* for divisible coins or tokens, the value in this field is to be divided by 100,000,000 (e.g. 1 represents 0.00000001 MSC, 100,000,000 represents 1.0 MSC), which allows for the number of Master Protocol coins or tokens to be specified with the same precision as bitcoins (eight decimal places)
Expand Down Expand Up @@ -336,8 +341,10 @@ This section defines the fields that are used to construct transaction messages.
* 11: [Mark a Savings Address as Compromised](#marking-a-savings-address-as-compromised)
* 12: [Mark an Address as Rate-Limited](#marking-an-address-as-rate-limited)
* 14: [Remove a Rate Limitation](#removing-a-rate-limitation)
* 30: [Register a Data Stream](#registering-a-data-stream)
* 31: [Publish Data](#publishing-data)
* 30: [Register a Data Stream](#registering-a-data-stream)
* 31: [Publish Data](#publishing-data)
* 32: [Create a List of Addresses](#create-a-list-of-addresses)
* 33: [Removing Addresses from a List](#removing-addresses-from-a-list)
* 40: [Offer/Accept a Bet](#offering-a-bet)
* 60: [List Something for Sale](#listing-something-for-sale)
* 61: [Initiate a Purchase from a Listing](#initiating-a-purchase)
Expand Down Expand Up @@ -606,7 +613,9 @@ Any time the name of a property is displayed, the ID number of the property must

To help distinguish legitimate companies and ventures from scams, spam, and experiments, the Master Protocol allows users to spend Mastercoins for the purpose of promoting a smart property. When UI clients display smart properties, the default ordering should be based on how many Mastercoins have been spent for promoting the property, adjusted for how long ago the Mastercoins were spent. Details on promoting a smart property by spending Mastercoins and how that affects sort ordering can be found below.

The "Property Data" field is general-purpose text, but can be used for things like storing the hash of a contract to ensure it is in the block-chain at property creation (i.e. "Proof of Existence").
The "Property Data" field is general-purpose text, but can be used for things like storing the hash of a contract to ensure it is in the block-chain at property creation (i.e. "Proof of Existence").

All property creation transaction types (i.e. 50, 51, 54) can be restricted such that only a specified list of addresses can use the resulting property tokens. This can be useful when the issuer wants to restrict their token to a set of approved people, such as those who have provided identifying documentation in compliance with KYC (know your customer) AML (anti-money-laundering) laws. When creating a property which should be restricted to a set of addresses, simply set the reference address to be the address which created the list of approved addresses. Addresses which are not on the list will not be able to receive or otherwise interact with the token (transactions attempting to do so are invalid). However, addresses which are removed from the list can still send their restricted tokens to another approved address using simple send, but they cannot receive new coins or use the coins in any other way. This prevents tokens from effectively being destroyed when addresses are removed from the approved list. To create a list of addresses, see [Create a List of Addresses](#create-a-list-of-addresses) later in this document.

### New Property Creation with Fixed number of Tokens

Expand Down Expand Up @@ -847,7 +856,42 @@ Say that your project is finished and you want to start burning tokens in exchan

# Future Transactions

The transactions below are still subject to revision and therefore are not included in deployments based on this version of the spec.
The transactions below are still subject to revision and therefore are not included in deployments based on this version of the spec.

## Creating a List of Addresses

The Master Protocol allows the creation of a list of addresses which can then be referenced by other transactions. For instance, some tokens may be restricted to only be used by a set of approved addresses, such as addresses of people who have provided identifying documentation in compliance with KYC (know your customer) AML (anti-money-laundering) laws. See the introduction to [Smart Property](#smart-property) above for details on how to restrict a token to a set of addresses.

To create or append a list of addresses, publish the following notification from the address which will maintain the list:

| **Field** | **Type** | **Example** |
| ---- | ---- | ---- |
| Transaction version |[Transaction version](#field-transaction-version) | 0 |
| Transaction type | [Transaction type](#field-transaction-type) | 32|
| Number of addresses | [Integer one-byte](#field-integer-one-byte) | 4|
| Address 1 | [Bitcoin Address](#field-bitcoin-address) | 010966776006953D5567439E5E39F86A0D273BEE |
| Address 2 | [Bitcoin Address](#field-bitcoin-address) | 010966776006953D5567439E5E39F86A0D273BED |
| Address 3 | [Bitcoin Address](#field-bitcoin-address) | 010966776006953D5567439E5E39F86A0D273BEC |
| Address 4 | [Bitcoin Address](#field-bitcoin-address) | 010966776006953D5567439E5E39F86A0D273BEB |

That transaction effectively starts the list (or appends it), and provides a handle to refer to the list (the address which published this message). Note that this transaction could be massive if a lot of addresses are added, and may require large fees in bitcoins. Additionally, 0.00000001 MSC (smallest unit of MSC) are burned for each address added, so the address maintaining the list must have enough MSC and BTC on hand to cover these fees.


## Removing Addresses from a List

To remove addresses from a list, publish the following notification from the address which maintains the list:

| **Field** | **Type** | **Example** |
| ---- | ---- | ---- |
| Transaction version |[Transaction version](#field-transaction-version) | 0 |
| Transaction type | [Transaction type](#field-transaction-type) | 33|
| Number of addresses | [Integer one-byte](#field-integer-one-byte) |2|
| Address 1 | [Bitcoin Address](#field-bitcoin-address) | 010966776006953D5567439E5E39F86A0D273BEE |
| Address 2 | [Bitcoin Address](#field-bitcoin-address) | 010966776006953D5567439E5E39F86A0D273BED |

Any referenced addresses are removed from the list. Note that as with the previous transaction type, this transaction could be massive if a lot of addresses are removed, and may require large fees in bitcoins. Additionally, 0.00000001 MSC (smallest unit of MSC) are burned for each address removed, so the address maintaining the list must have enough MSC and BTC on hand to cover these fees.



## Transactions to Limit Funds (Theft Prevention)

Expand Down