diff --git a/README.rst b/README.rst index 94d9db3a..7211ee6d 100644 --- a/README.rst +++ b/README.rst @@ -57,7 +57,7 @@ Index of ZIPs 203 Transaction Expiry Final 205 Deployment of the Sapling Network Upgrade Final 206 Deployment of the Blossom Network Upgrade Final - 207 Split Founders' Reward Withdrawn + 207 Funding Streams Draft 208 Shorter Block Target Spacing Final 209 Prohibit Negative Shielded Value Pool Final 210 Sapling Anchor Deduplication within Transactions Draft diff --git a/css/style.css b/css/style.css index 36c73f23..158b07d6 100644 --- a/css/style.css +++ b/css/style.css @@ -255,7 +255,7 @@ td:first-child { width: 920px; } pre, div.math, table { - font-size: 0.9375rem; + font-size: 0.85rem; } } diff --git a/index.html b/index.html index 76d4d486..8ab8fe37 100644 --- a/index.html +++ b/index.html @@ -36,7 +36,7 @@ 203 Transaction Expiry Final 205 Deployment of the Sapling Network Upgrade Final 206 Deployment of the Blossom Network Upgrade Final - 207 Split Founders' Reward Withdrawn + 207 Funding Streams Draft 208 Shorter Block Target Spacing Final 209 Prohibit Negative Shielded Value Pool Final 210 Sapling Anchor Deduplication within Transactions Draft diff --git a/zip-0207.html b/zip-0207.html index 87779052..026bb7aa 100644 --- a/zip-0207.html +++ b/zip-0207.html @@ -1,52 +1,70 @@ - ZIP 207: Split Founders' Reward + ZIP 207: Funding Streams 
ZIP: 207
-Title: Split Founders' Reward
+Title: Funding Streams
 Owners: Jack Grigg <str4d@electriccoin.co>
+        Daira Hopwood <daira@electriccoin.co>
 Category: Consensus
-Status: Withdrawn
+Status: Draft
 Created: 2019-01-04
 License: MIT

Terminology

The key words "MUST", "SHOULD", "SHOULD NOT", and "MAY" in this document are to be interpreted as described in RFC 2119. 1

+

The terms "block subsidy" and "halving" in this document are to be interpreted as described in sections 3.9 and 7.7 of the Zcash Protocol Specification. 3 5

+

The terms below are to be interpreted as follows:

+
+
${NU4}
+
Code-name for the fifth Zcash network upgrade, also known as Network Upgrade 4.
+
Testnet
+
The Zcash test network, as defined in the Zcash Protocol Specification. 2
+
Mainnet
+
The Zcash production network, as defined in the Zcash Protocol Specification. 2
+

Abstract

-

This Withdrawn proposal would have altered consensus rules to split the original Founders' Reward across several recipient addresses per block instead of one, corresponding to the several funding streams contained within it.

+

This proposal specifies a mechanism to support funding streams, distributed from a portion of the block subsidy for a specified range of block heights.

+

This is intended as a means of implementing the Zcash Development Fund, using the funding stream definitions specified in ZIP 214 10. It should be read in conjunction with ZIP 1014 12, which describes the high-level requirements for that fund.

Motivation

-

Since the launch of the Zcash network, the consensus rules have required that until the first block reward halving (at block 850,000), each block must send 20% of the block subsidy to a hard-coded transparent address. 2 This funding stream is referred to as the Founders' Reward.

-

This stream of 2.5-ZEC outputs (the value after the mining slow-start was completed) can be split into several logical funding streams (for background, see 3). Modifying the consensus rules to allocate the 2.5 ZEC across separate recipient addresses decouples these funding streams organizationally, legally, and operationally. It further reinforces transparency as to the structure of the original Founders' Reward.

+

Motivation for the Zcash Development Fund is considered in ZIP 1014 12.

+

This ZIP 207 was originally proposed for the Blossom network upgrade, as a means of splitting the original Founders' Reward into several streams. It was then withdrawn when such splitting was judged to be unnecessary at the consensus level. Since the capabilities of the funding stream mechanism match the requirements for the Zcash Development Fund, the ZIP is being reintroduced for that purpose in order to reuse specification, analysis, and implementation effort.

+
+

Requirements

+

The primary requirement of this ZIP is to provide a mechanism for specifying the funding streams that are used in ZIP 214 [#zip-0214] to implement the Zcash Development Fund. It should be sufficiently expressive to handle both the main three "slices" (ECC, ZF, and MG) defined in ZIP 1014 12, and also (with additional funding stream definitions) the "direct grant option" described in that ZIP.

+

As for the original Founders' Reward, addresses for a given funding stream are changed on a roughly-monthly basis, so that keys that are not yet needed may be kept off-line as a security measure.

Specification

Definitions

-

We use the following constants and functions defined in 4:

+

We use the following constants and functions defined in 4, 5, and 6:

  • BlossomActivationHeight
  • PostBlossomHalvingInterval
  • Halving(height)
    • +
  • BlockSubsidy(height)
    • +
  • RedeemScriptHash(height).
-

We also define the following constants and functions:

+

We also define the following function:

    -
  • SlowStartShift as-defined in 2.
  • HeightForHalving(halving): Smallest height such that Halving(height) = halving

Funding streams

-

A funding stream is defined by a block reward fraction (represented as a numerator and a denominator), a start height (inclusive), and an end height (exclusive).

-

By defining the issuance as a proportion of the total block issuance, rather than absolute zatoshis, this ZIP dovetails with any changes to both block target times and issuance-per-block rates while maintaining an unchanged target-time-based issuance schedule. We anticipate such target-time / issuance rate changes in other ZIPs (for example, 4).

+

A funding stream is defined by a block subsidy fraction (represented as a numerator and a denominator), a start height (inclusive), and an end height (exclusive).

+

By defining the issuance as a proportion of the total block subsidy, rather than absolute zatoshis, this ZIP dovetails with any changes to both block target spacing and issuance-per-block rates, while maintaining an unchanged target-time-based issuance schedule. Such a target-time / issuance rate change occurred at the Blossom network upgrade, for example. 8

The value of a funding stream at a given block height is defined as:

FundingStream[FUND].Value(height) =
     floor((
-        BlockReward(height) * FundingStream[FUND].ValueNumerator
+        BlockSubsidy(height) * FundingStream[FUND].ValueNumerator
     ) / FundingStream[FUND].ValueDenominator)

An active funding stream at a given block height is defined as a funding stream for which the block height is less than its end height, but not less than its start height.

-

Each funding stream has an associated set of recipient addresses. Each address is used for at most 1/48th of a halving interval, creating a roughly-monthly sequence of funding periods. The address to be used for a given block height is defined as follows:

+

Each funding stream has an associated sequence of recipient addresses, each of which MUST be either a transparent P2SH address or a Sapling address.

+

Each address is used for at most 1/48th of a halving interval, creating a roughly-monthly sequence of funding periods. The address to be used for a given block height is defined as follows:

AddressChangeInterval = PostBlossomHalvingInterval / 48
 AddressPeriod(height) =
     floor((
@@ -57,311 +75,116 @@ FundingStream[FUND].AddressIndex(height) =
 Address(height) = FundingStream[FUND].Addresses[FundingStream[FUND].AddressIndex(height)]

This has the property that all active funding streams change the address they are using on the same block height schedule, aligned to the height of the first halving so that 48 funding periods fit cleanly within a halving interval. This can be leveraged to simplify implementations, by batching the necessary outputs for each funding period.

Below is a visual representation of how stream addresses align with funding periods:

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Example heightStream AStream BStream C
AddressChangeInterval - 2A0
AddressChangeInterval - 1A0
AddressChangeIntervalA1B0C0
AddressChangeInterval + 1A1B0C0
...
2*AddressChangeInterval - 2A1B0C0
2*AddressChangeInterval - 1A1B0C0
2*AddressChangeIntervalA2C1
2*AddressChangeInterval + 1A2C1
...
PostBlossomHalvingInterval - 2A2C1
PostBlossomHalvingInterval - 1A2C1
PostBlossomHalvingIntervalC2
PostBlossomHalvingInterval + 1C2
-

Note that this is not intended to align with the end of a pre-Blossom Founders' Reward address period (as defined by FounderAddressChangeInterval in 5). There will be a shortened Founders' Reward address period prior to Blossom activation.

+
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
Example heightStream AStream BStream C
AddressChangeInterval - 2A0
AddressChangeInterval - 1A0
AddressChangeIntervalA1B0C0
AddressChangeInterval + 1A1B0C0
...
2*AddressChangeInterval - 2A1B0C0
2*AddressChangeInterval - 1A1B0C0
2*AddressChangeIntervalA2C1
2*AddressChangeInterval + 1A2C1
...
PostBlossomHalvingInterval - 2A2C1
PostBlossomHalvingInterval - 1A2C1
PostBlossomHalvingIntervalC2
PostBlossomHalvingInterval + 1C2
+
+

On Mainnet, ${NU4} is planned to activate exactly at the point when the Founders' Reward expires, at block height 1046400. On Testnet, there will be a shortened Founders' Reward address period prior to ${NU4} activation.

Consensus rules

-

Prior to activation of the Blossom network upgrade, the existing consensus rule for payment of the original Founders' Reward is enforced. 5

-

Once the Blossom network upgrade activates:

+

Prior to activation of the ${NU4} network upgrade, the existing consensus rule for payment of the original Founders' Reward is enforced. 6

+

Once the ${NU4} network upgrade activates:

    -
  • The existing consensus rule 5 is no longer active.
    • -
  • The coinbase transaction in each block MUST contain at least one output per active funding stream that pays the stream's value to the stream's recipient address for the block's height.
    • -
-
-

Stream definitions

-

The consensus-defined funding streams described above each start at the Blossom activation height, and end at the first block reward halving. They are defined as follows:

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
StreamValue numeratorValue denominatorStart heightEnd height
FS 1340BlossomActivationHeightHeightForHalving(1)
FS 2125BlossomActivationHeightHeightForHalving(1)
FS 3140BlossomActivationHeightHeightForHalving(1)
FS 4150BlossomActivationHeightHeightForHalving(1)
FS 5180BlossomActivationHeightHeightForHalving(1)
FS 6180BlossomActivationHeightHeightForHalving(1)
FS 71100BlossomActivationHeightHeightForHalving(1)
FS 81200BlossomActivationHeightHeightForHalving(1)
-
    -
  • To-do: specify the correct values.
    • -
-

The sum of the block reward fractions for the above funding streams is 1/5, equal to the original Founders' Reward (as-defined by FoundersFraction in 6).

-

The sets of recipient addresses are defined as follows:

- 
std::vector<std::string> FS_1_ADDRESSES = [
-    "tFS1INVALIDADDRESS00",
-    "tFS1INVALIDADDRESS01",
-    "tFS1INVALIDADDRESS02",
-    "tFS1INVALIDADDRESS03",
-    "tFS1INVALIDADDRESS04",
-    "tFS1INVALIDADDRESS05",
-    "tFS1INVALIDADDRESS06",
-    "tFS1INVALIDADDRESS07",
-    "tFS1INVALIDADDRESS08",
-    "tFS1INVALIDADDRESS09",
-    "tFS1INVALIDADDRESS10",
-    "tFS1INVALIDADDRESS11",
-];
-
-std::vector<std::string> FS_2_ADDRESSES = [
-    "tFS2INVALIDADDRESS00",
-    "tFS2INVALIDADDRESS01",
-    "tFS2INVALIDADDRESS02",
-    "tFS2INVALIDADDRESS03",
-    "tFS2INVALIDADDRESS04",
-    "tFS2INVALIDADDRESS05",
-    "tFS2INVALIDADDRESS06",
-    "tFS2INVALIDADDRESS07",
-    "tFS2INVALIDADDRESS08",
-    "tFS2INVALIDADDRESS09",
-    "tFS2INVALIDADDRESS10",
-    "tFS2INVALIDADDRESS11",
-];
-
-std::vector<std::string> FS_3_ADDRESSES = [
-    "tFS3INVALIDADDRESS00",
-    "tFS3INVALIDADDRESS01",
-    "tFS3INVALIDADDRESS02",
-    "tFS3INVALIDADDRESS03",
-    "tFS3INVALIDADDRESS04",
-    "tFS3INVALIDADDRESS05",
-    "tFS3INVALIDADDRESS06",
-    "tFS3INVALIDADDRESS07",
-    "tFS3INVALIDADDRESS08",
-    "tFS3INVALIDADDRESS09",
-    "tFS3INVALIDADDRESS10",
-    "tFS3INVALIDADDRESS11",
-];
-
-std::vector<std::string> FS_4_ADDRESSES = [
-    "tFS4INVALIDADDRESS00",
-    "tFS4INVALIDADDRESS01",
-    "tFS4INVALIDADDRESS02",
-    "tFS4INVALIDADDRESS03",
-    "tFS4INVALIDADDRESS04",
-    "tFS4INVALIDADDRESS05",
-    "tFS4INVALIDADDRESS06",
-    "tFS4INVALIDADDRESS07",
-    "tFS4INVALIDADDRESS08",
-    "tFS4INVALIDADDRESS09",
-    "tFS4INVALIDADDRESS10",
-    "tFS4INVALIDADDRESS11",
-];
-
-std::vector<std::string> FS_5_ADDRESSES = [
-    "tFS5INVALIDADDRESS00",
-    "tFS5INVALIDADDRESS01",
-    "tFS5INVALIDADDRESS02",
-    "tFS5INVALIDADDRESS03",
-    "tFS5INVALIDADDRESS04",
-    "tFS5INVALIDADDRESS05",
-    "tFS5INVALIDADDRESS06",
-    "tFS5INVALIDADDRESS07",
-    "tFS5INVALIDADDRESS08",
-    "tFS5INVALIDADDRESS09",
-    "tFS5INVALIDADDRESS10",
-    "tFS5INVALIDADDRESS11",
-];
-
-std::vector<std::string> FS_6_ADDRESSES = [
-    "tFS6INVALIDADDRESS00",
-    "tFS6INVALIDADDRESS01",
-    "tFS6INVALIDADDRESS02",
-    "tFS6INVALIDADDRESS03",
-    "tFS6INVALIDADDRESS04",
-    "tFS6INVALIDADDRESS05",
-    "tFS6INVALIDADDRESS06",
-    "tFS6INVALIDADDRESS07",
-    "tFS6INVALIDADDRESS08",
-    "tFS6INVALIDADDRESS09",
-    "tFS6INVALIDADDRESS10",
-    "tFS6INVALIDADDRESS11",
-];
-
-std::vector<std::string> FS_7_ADDRESSES = [
-    "tFS7INVALIDADDRESS00",
-    "tFS7INVALIDADDRESS01",
-    "tFS7INVALIDADDRESS02",
-    "tFS7INVALIDADDRESS03",
-    "tFS7INVALIDADDRESS04",
-    "tFS7INVALIDADDRESS05",
-    "tFS7INVALIDADDRESS06",
-    "tFS7INVALIDADDRESS07",
-    "tFS7INVALIDADDRESS08",
-    "tFS7INVALIDADDRESS09",
-    "tFS7INVALIDADDRESS10",
-    "tFS7INVALIDADDRESS11",
-];
-
-std::vector<std::string> FS_8_ADDRESSES = [
-    "tFS8INVALIDADDRESS00",
-    "tFS8INVALIDADDRESS01",
-    "tFS8INVALIDADDRESS02",
-    "tFS8INVALIDADDRESS03",
-    "tFS8INVALIDADDRESS04",
-    "tFS8INVALIDADDRESS05",
-    "tFS8INVALIDADDRESS06",
-    "tFS8INVALIDADDRESS07",
-    "tFS8INVALIDADDRESS08",
-    "tFS8INVALIDADDRESS09",
-    "tFS8INVALIDADDRESS10",
-    "tFS8INVALIDADDRESS11",
-];
-
    -
  • To-do: specify the correct sets of FR addresses.
    • -
  • To-do: require that the FR address sets are PGP-signed with appropriate keys.
    • +
  • The existing consensus rule 6 is no longer active. (This would be the case under the preexisting consensus rules for Mainnet, but not for Testnet.)
    • +
  • The coinbase transaction in each block MUST contain at least one output per active funding stream that pays the stream's value in the prescribed way to the stream's recipient address for the block's height.
    • +
  • The "prescribed way" to pay a transparent P2SH address is to use a standard P2SH script of the form OP_HASH160 RedeemScriptHash(height) OP_EQUAL as the scriptPubKey.
    • +
  • The "prescribed way" to pay a Sapling address is as defined in 9. That is, all Sapling outputs in coinbase transactions (including, but not limited to, outputs for funding streams) MUST have valid note commitments when recovered using a 32-byte array of zeroes as the outgoing viewing key.
+

For the funding stream definitions to be activated at ${NU4}, see ZIP 214. 10 Funding stream definitions can be added, changed, or deleted in ZIPs associated with subsequent network upgrades, subject to the ZIP process. 7

Example implementation 

struct FundingPeriod {
@@ -373,14 +196,9 @@ Address(height) = FundingStream[FUND].Addresses[FundingStream[FUND].AddressIndex
 };
 
 enum FundingStream {
-    FS_1,
-    FS_2,
-    FS_3,
-    FS_4,
-    FS_5,
-    FS_6,
-    FS_7,
-    FS_8,
+    FS_ECC,
+    FS_ZF,
+    FS_MG,
     MAX_FUNDING_STREAMS,
 };
 
@@ -413,14 +231,9 @@ Address(height) = FundingStream[FUND].Addresses[FundingStream[FUND].AddressIndex
 
     consensus.nFundingPeriodLength = consensus.nSubsidyPostBlossomHalvingInterval / 48;
 
-    AddZIP207FundingStream(consensus, Consensus::FS_1, FS_1_ADDRESSES, 3, 40);
-    AddZIP207FundingStream(consensus, Consensus::FS_2, FS_2_ADDRESSES, 1, 25);
-    AddZIP207FundingStream(consensus, Consensus::FS_3, FS_3_ADDRESSES, 1, 40);
-    AddZIP207FundingStream(consensus, Consensus::FS_4, FS_4_ADDRESSES, 1, 50);
-    AddZIP207FundingStream(consensus, Consensus::FS_5, FS_5_ADDRESSES, 1, 80);
-    AddZIP207FundingStream(consensus, Consensus::FS_6, FS_6_ADDRESSES, 1, 80);
-    AddZIP207FundingStream(consensus, Consensus::FS_7, FS_7_ADDRESSES, 1, 100);
-    AddZIP207FundingStream(consensus, Consensus::FS_8, FS_8_ADDRESSES, 1, 200);
+    AddZIP207FundingStream(consensus, Consensus::FS_ECC, FS_ECC_ADDRESSES, 7, 100);
+    AddZIP207FundingStream(consensus, Consensus::FS_ZF,  FS_ZF_ADDRESSES,  5, 100);
+    AddZIP207FundingStream(consensus, Consensus::FS_MG,  FS_MG_ADDRESSES,  8, 100);
 
     ...
 }
@@ -476,7 +289,7 @@ Address(height) = FundingStream[FUND].Addresses[FundingStream[FUND].AddressIndex
 {
     ...
 
-    if (NetworkUpgradeActive(nHeight, consensusParams, Consensus::UPGRADE_BLOSSOM)) {
+    if (NetworkUpgradeActive(nHeight, consensusParams, Consensus::UPGRADE_NU4)) {
         // Coinbase transaction must include outputs corresponding to the consensus
         // funding streams active at the current block height.
         auto requiredStreams = GetActiveFundingStreams(nHeight, consensusParams);
@@ -491,14 +304,15 @@ Address(height) = FundingStream[FUND].Addresses[FundingStream[FUND].AddressIndex
         }
 
         if (!requiredStreams.empty()) {
-            return state.DoS(100, error("%s: funding stream missing", __func__), REJECT_INVALID, "cb-funding-stream-missing");
+            return state.DoS(100, error("%s: funding stream missing", __func__),
+                             REJECT_INVALID, "cb-funding-stream-missing");
         }
     } else {
         // Coinbase transaction must include an output sending 20% of
-        // the block reward to a founders reward script, until the last founders
+        // the block subsidy to a Founders' Reward script, until the last founders
         // reward block is reached, with exception of the genesis block.
-        // The last founders reward block is defined as the block just before the
-        // first subsidy halving block, which occurs at halving_interval + slow_start_shift
+        // The last Founders' Reward block is defined as the block just before the
+        // first subsidy halving block.
         if ((nHeight > 0) && (nHeight <= consensusParams.GetLastFoundersRewardBlockHeight())) {
             bool found = false;
 
@@ -512,7 +326,8 @@ Address(height) = FundingStream[FUND].Addresses[FundingStream[FUND].AddressIndex
             }
 
             if (!found) {
-                return state.DoS(100, error("%s: founders reward missing", __func__), REJECT_INVALID, "cb-no-founders-reward");
+                return state.DoS(100, error("%s: founders reward missing", __func__),
+                                 REJECT_INVALID, "cb-no-founders-reward");
             }
         }
     }
@@ -522,15 +337,10 @@ Address(height) = FundingStream[FUND].Addresses[FundingStream[FUND].AddressIndex

Deployment

-

This proposal was originally intended to be deployed with the Blossom network upgrade. 7

+

This proposal is intended to be deployed with ${NU4}. 11

Backward compatibility

This proposal intentionally creates what is known as a "bilateral consensus rule change". Use of this mechanism requires that all network participants upgrade their software to a compatible version within the upgrade window. Older software will treat post-upgrade blocks as invalid, and will follow any pre-upgrade branch that persists.

-

This proposal is designed with the explicit requirement of not altering the overall issuance schedule (based on time), nor does it alter the proportion or timeline of the overall Founders' Reward. As a result, no users outside of the Zerocoin Electric Coin Company and Zcash Foundation should experience any UX or economic change outside of the upgrade due to this proposal itself.

-

Interactions with other ZIPs

-

4 (Shorter Block Target Spacing) specifies a change to the block target spacing. It is planned to take effect in the Blossom network upgrade 7. This ZIP was originally written to take effect at the same time, but was Withdrawn from consideration for Blossom.

-

ZIP 208 modifies the payment of the original Founders' Reward to take account of the block target spacing change. It does this by specifying a FounderAddressAdjustedHeight function and related changes, which would need to be revisited to take into account funding streams.

-

Reference Implementation

TBC

@@ -544,51 +354,91 @@ Address(height) = FundingStream[FUND].Addresses[FundingStream[FUND].AddressIndex - +
- +
2Section 7.7: Calculation of Block Subsidy and Founders' Reward. Zcash Protocol Specification, Version 2018.0-beta-33 or later [Overwinter+Sapling]Zcash Protocol Specification, Version 2020.1.1 or later
- +
- - - -
3Continued Funding and Transparency
- - - - - - - -
4ZIP 208: Shorter Block Target Spacing
- - - - - +
5Section 7.8: Payment of Founders' Reward. Zcash Protocol Specification, Version 2018.0-beta-33 or later [Overwinter+Sapling]Section 3.9: Block Subsidy and Founders' Reward. Zcash Protocol Specification, Version 2020.1.1 or later
- - + +
6Section 5.3: Constants. Zcash Protocol Specification, Version 2018.0-beta-33 or later [Overwinter+Sapling]4Section 5.3: Constants. Zcash Protocol Specification, Version 2020.1.1 or later
- +
+ + + + + + +
5Section 7.7: Calculation of Block Subsidy and Founders' Reward. Zcash Protocol Specification, Version 2020.1.1 or later
+ + + + + + + +
6Section 7.8: Payment of Founders' Reward. Zcash Protocol Specification, Version 2020.1.1 or later
+ - + + + +
7ZIP 206: Blossom Network UpgradeZIP 0: ZIP Process
+ + + + + + + +
8ZIP 208: Shorter Block Target Spacing
+ + + + + + + +
9ZIP 213: Shielded Coinbase
+ + + + + + + +
10ZIP 214: Consensus rules for a Zcash Development Fund
+ + + + + + + +
11ZIP 251: Deployment of the ${NU4} Network Upgrade
+ + + + +
12ZIP 1014: Establishing a Dev Fund for ECC, ZF, and Major Grants
diff --git a/zip-0207.rst b/zip-0207.rst index 545c9587..93d202a0 100644 --- a/zip-0207.rst +++ b/zip-0207.rst @@ -1,10 +1,11 @@ :: ZIP: 207 - Title: Split Founders' Reward + Title: Funding Streams Owners: Jack Grigg + Daira Hopwood Category: Consensus - Status: Withdrawn + Status: Draft Created: 2019-01-04 License: MIT @@ -15,26 +16,59 @@ Terminology The key words "MUST", "SHOULD", "SHOULD NOT", and "MAY" in this document are to be interpreted as described in RFC 2119. [#RFC2119]_ +The terms "block subsidy" and "halving" in this document are to be interpreted +as described in sections 3.9 and 7.7 of the Zcash Protocol Specification. +[#protocol-subsidyconcepts]_ [#protocol-subsidies]_ + +The terms below are to be interpreted as follows: + +${NU4} + Code-name for the fifth Zcash network upgrade, also known as Network Upgrade 4. +Testnet + The Zcash test network, as defined in the Zcash Protocol Specification. [#protocol]_ +Mainnet + The Zcash production network, as defined in the Zcash Protocol Specification. [#protocol]_ + Abstract ======== -This Withdrawn proposal would have altered consensus rules to split the original Founders' Reward across -several recipient addresses per block instead of one, corresponding to the several funding streams contained -within it. +This proposal specifies a mechanism to support funding streams, distributed +from a portion of the block subsidy for a specified range of block heights. + +This is intended as a means of implementing the Zcash Development Fund, +using the funding stream definitions specified in ZIP 214 [#zip-0214]_. It +should be read in conjunction with ZIP 1014 [#zip-1014]_, which describes +the high-level requirements for that fund. Motivation ========== -Since the launch of the Zcash network, the consensus rules have required that until the first block reward -halving (at block 850,000), each block must send 20% of the block subsidy to a hard-coded transparent address. -[#block-subsidy]_ This funding stream is referred to as the Founders' Reward. +Motivation for the Zcash Development Fund is considered in ZIP 1014 [#zip-1014]_. -This stream of 2.5-ZEC outputs (the value after the mining slow-start was completed) can be split into several -logical funding streams (for background, see [#continued-funding]_). Modifying the consensus rules to allocate -the 2.5 ZEC across separate recipient addresses decouples these funding streams organizationally, legally, and -operationally. It further reinforces transparency as to the structure of the original Founders' Reward. +This ZIP 207 was originally proposed for the Blossom network upgrade, as a +means of splitting the original Founders' Reward into several streams. It was +then withdrawn when such splitting was judged to be unnecessary at the consensus +level. Since the capabilities of the funding stream mechanism match the +requirements for the Zcash Development Fund, the ZIP is being reintroduced +for that purpose in order to reuse specification, analysis, and implementation +effort. + + +Requirements +============ + +The primary requirement of this ZIP is to provide a mechanism for specifying +the funding streams that are used in ZIP 214 [#zip-0214] to implement the Zcash +Development Fund. It should be sufficiently expressive to handle both the main +three "slices" (ECC, ZF, and MG) defined in ZIP 1014 [#zip-1014]_, and also +(with additional funding stream definitions) the "direct grant option" described +in that ZIP. + +As for the original Founders' Reward, addresses for a given funding stream are +changed on a roughly-monthly basis, so that keys that are not yet needed may be +kept off-line as a security measure. Specification @@ -43,42 +77,48 @@ Specification Definitions ----------- -We use the following constants and functions defined in [#zip-0208]_: +We use the following constants and functions defined in [#protocol-constants]_, +[#protocol-subsidies]_, and [#protocol-foundersreward]_: - ``BlossomActivationHeight`` - ``PostBlossomHalvingInterval`` - ``Halving(height)`` +- ``BlockSubsidy(height)`` +- ``RedeemScriptHash(height)``. -We also define the following constants and functions: +We also define the following function: + +- ``HeightForHalving(halving)``: Smallest ``height`` such that + ``Halving(height) = halving`` -- ``SlowStartShift`` as-defined in [#block-subsidy]_. -- ``HeightForHalving(halving)``: Smallest ``height`` such that ``Halving(height) = halving`` Funding streams --------------- -A funding stream is defined by a block reward fraction (represented as a +A funding stream is defined by a block subsidy fraction (represented as a numerator and a denominator), a start height (inclusive), and an end height (exclusive). -By defining the issuance as a proportion of the total block issuance, rather +By defining the issuance as a proportion of the total block subsidy, rather than absolute zatoshis, this ZIP dovetails with any changes to both block -target times and issuance-per-block rates while maintaining an unchanged -target-time-based issuance schedule. We anticipate such target-time / issuance -rate changes in other ZIPs (for example, [#zip-0208]_). +target spacing and issuance-per-block rates, while maintaining an unchanged +target-time-based issuance schedule. Such a target-time / issuance rate change +occurred at the Blossom network upgrade, for example. [#zip-0208]_ The value of a funding stream at a given block height is defined as:: FundingStream[FUND].Value(height) = floor(( - BlockReward(height) * FundingStream[FUND].ValueNumerator + BlockSubsidy(height) * FundingStream[FUND].ValueNumerator ) / FundingStream[FUND].ValueDenominator) An active funding stream at a given block height is defined as a funding stream for which the block height is less than its end height, but not less than its start height. -Each funding stream has an associated set of recipient addresses. +Each funding stream has an associated sequence of recipient addresses, +each of which MUST be either a transparent P2SH address or a Sapling address. + Each address is used for at most 1/48th of a halving interval, creating a roughly-monthly sequence of funding periods. The address to be used for a given block height is defined as follows:: @@ -101,193 +141,59 @@ necessary outputs for each funding period. Below is a visual representation of how stream addresses align with funding periods: -================================== ======== ======== ======== - Example height Stream A Stream B Stream C -================================== ======== ======== ======== - ``AddressChangeInterval - 2`` A0 - ``AddressChangeInterval - 1`` A0 - ``AddressChangeInterval`` A1 B0 C0 - ``AddressChangeInterval + 1`` A1 B0 C0 - \... - ``2*AddressChangeInterval - 2`` A1 B0 C0 - ``2*AddressChangeInterval - 1`` A1 B0 C0 - ``2*AddressChangeInterval`` A2 C1 - ``2*AddressChangeInterval + 1`` A2 C1 - \... -``PostBlossomHalvingInterval - 2`` A2 C1 -``PostBlossomHalvingInterval - 1`` A2 C1 -``PostBlossomHalvingInterval`` C2 -``PostBlossomHalvingInterval + 1`` C2 -================================== ======== ======== ======== + ================================== ======== ======== ======== + Example height Stream A Stream B Stream C + ================================== ======== ======== ======== + ``AddressChangeInterval - 2`` A0 + ``AddressChangeInterval - 1`` A0 + ``AddressChangeInterval`` A1 B0 C0 + ``AddressChangeInterval + 1`` A1 B0 C0 + \... + ``2*AddressChangeInterval - 2`` A1 B0 C0 + ``2*AddressChangeInterval - 1`` A1 B0 C0 + ``2*AddressChangeInterval`` A2 C1 + ``2*AddressChangeInterval + 1`` A2 C1 + \... + ``PostBlossomHalvingInterval - 2`` A2 C1 + ``PostBlossomHalvingInterval - 1`` A2 C1 + ``PostBlossomHalvingInterval`` C2 + ``PostBlossomHalvingInterval + 1`` C2 + ================================== ======== ======== ======== + +On Mainnet, ${NU4} is planned to activate exactly at the point when the Founders' +Reward expires, at block height 1046400. On Testnet, there will be a shortened +Founders' Reward address period prior to ${NU4} activation. -Note that this is not intended to align with the end of a pre-Blossom Founders' Reward address period (as -defined by ``FounderAddressChangeInterval`` in [#original-fr-consensus-rule]_). There will be a shortened -Founders' Reward address period prior to Blossom activation. Consensus rules --------------- -Prior to activation of the Blossom network upgrade, the existing consensus rule -for payment of the original Founders' Reward is enforced. [#original-fr-consensus-rule]_ +Prior to activation of the ${NU4} network upgrade, the existing consensus rule +for payment of the original Founders' Reward is enforced. [#protocol-foundersreward]_ -Once the Blossom network upgrade activates: +Once the ${NU4} network upgrade activates: + +- The existing consensus rule [#protocol-foundersreward]_ is no longer active. + (This would be the case under the preexisting consensus rules for Mainnet, but + not for Testnet.) -- The existing consensus rule [#original-fr-consensus-rule]_ is no longer - active. - The coinbase transaction in each block MUST contain at least one output per - active funding stream that pays the stream's value to the stream's recipient - address for the block's height. + active funding stream that pays the stream's value in the prescribed way to + the stream's recipient address for the block's height. -Stream definitions ------------------- +- The "prescribed way" to pay a transparent P2SH address is to use a standard + P2SH script of the form ``OP_HASH160 RedeemScriptHash(height) OP_EQUAL`` as + the ``scriptPubKey``. -The consensus-defined funding streams described above each start at the Blossom activation height, and end at -the first block reward halving. They are defined as follows: +- The "prescribed way" to pay a Sapling address is as defined in [#zip-0213]_. + That is, all Sapling outputs in coinbase transactions (including, but not + limited to, outputs for funding streams) MUST have valid note commitments + when recovered using a 32-byte array of zeroes as the outgoing viewing key. -====== =============== ================= =========================== ======================= -Stream Value numerator Value denominator Start height End height -====== =============== ================= =========================== ======================= - FS 1 3 40 ``BlossomActivationHeight`` ``HeightForHalving(1)`` - FS 2 1 25 ``BlossomActivationHeight`` ``HeightForHalving(1)`` - FS 3 1 40 ``BlossomActivationHeight`` ``HeightForHalving(1)`` - FS 4 1 50 ``BlossomActivationHeight`` ``HeightForHalving(1)`` - FS 5 1 80 ``BlossomActivationHeight`` ``HeightForHalving(1)`` - FS 6 1 80 ``BlossomActivationHeight`` ``HeightForHalving(1)`` - FS 7 1 100 ``BlossomActivationHeight`` ``HeightForHalving(1)`` - FS 8 1 200 ``BlossomActivationHeight`` ``HeightForHalving(1)`` -====== =============== ================= =========================== ======================= +For the funding stream definitions to be activated at ${NU4}, see ZIP 214. [#zip-0214]_ +Funding stream definitions can be added, changed, or deleted in ZIPs associated +with subsequent network upgrades, subject to the ZIP process. [#zip-0000]_ -- To-do: specify the correct values. - -The sum of the block reward fractions for the above funding streams is ``1/5``, equal to the original -Founders' Reward (as-defined by ``FoundersFraction`` in [#protocol-constants]_). - -The sets of recipient addresses are defined as follows: - -.. code:: cpp - - std::vector FS_1_ADDRESSES = [ - "tFS1INVALIDADDRESS00", - "tFS1INVALIDADDRESS01", - "tFS1INVALIDADDRESS02", - "tFS1INVALIDADDRESS03", - "tFS1INVALIDADDRESS04", - "tFS1INVALIDADDRESS05", - "tFS1INVALIDADDRESS06", - "tFS1INVALIDADDRESS07", - "tFS1INVALIDADDRESS08", - "tFS1INVALIDADDRESS09", - "tFS1INVALIDADDRESS10", - "tFS1INVALIDADDRESS11", - ]; - - std::vector FS_2_ADDRESSES = [ - "tFS2INVALIDADDRESS00", - "tFS2INVALIDADDRESS01", - "tFS2INVALIDADDRESS02", - "tFS2INVALIDADDRESS03", - "tFS2INVALIDADDRESS04", - "tFS2INVALIDADDRESS05", - "tFS2INVALIDADDRESS06", - "tFS2INVALIDADDRESS07", - "tFS2INVALIDADDRESS08", - "tFS2INVALIDADDRESS09", - "tFS2INVALIDADDRESS10", - "tFS2INVALIDADDRESS11", - ]; - - std::vector FS_3_ADDRESSES = [ - "tFS3INVALIDADDRESS00", - "tFS3INVALIDADDRESS01", - "tFS3INVALIDADDRESS02", - "tFS3INVALIDADDRESS03", - "tFS3INVALIDADDRESS04", - "tFS3INVALIDADDRESS05", - "tFS3INVALIDADDRESS06", - "tFS3INVALIDADDRESS07", - "tFS3INVALIDADDRESS08", - "tFS3INVALIDADDRESS09", - "tFS3INVALIDADDRESS10", - "tFS3INVALIDADDRESS11", - ]; - - std::vector FS_4_ADDRESSES = [ - "tFS4INVALIDADDRESS00", - "tFS4INVALIDADDRESS01", - "tFS4INVALIDADDRESS02", - "tFS4INVALIDADDRESS03", - "tFS4INVALIDADDRESS04", - "tFS4INVALIDADDRESS05", - "tFS4INVALIDADDRESS06", - "tFS4INVALIDADDRESS07", - "tFS4INVALIDADDRESS08", - "tFS4INVALIDADDRESS09", - "tFS4INVALIDADDRESS10", - "tFS4INVALIDADDRESS11", - ]; - - std::vector FS_5_ADDRESSES = [ - "tFS5INVALIDADDRESS00", - "tFS5INVALIDADDRESS01", - "tFS5INVALIDADDRESS02", - "tFS5INVALIDADDRESS03", - "tFS5INVALIDADDRESS04", - "tFS5INVALIDADDRESS05", - "tFS5INVALIDADDRESS06", - "tFS5INVALIDADDRESS07", - "tFS5INVALIDADDRESS08", - "tFS5INVALIDADDRESS09", - "tFS5INVALIDADDRESS10", - "tFS5INVALIDADDRESS11", - ]; - - std::vector FS_6_ADDRESSES = [ - "tFS6INVALIDADDRESS00", - "tFS6INVALIDADDRESS01", - "tFS6INVALIDADDRESS02", - "tFS6INVALIDADDRESS03", - "tFS6INVALIDADDRESS04", - "tFS6INVALIDADDRESS05", - "tFS6INVALIDADDRESS06", - "tFS6INVALIDADDRESS07", - "tFS6INVALIDADDRESS08", - "tFS6INVALIDADDRESS09", - "tFS6INVALIDADDRESS10", - "tFS6INVALIDADDRESS11", - ]; - - std::vector FS_7_ADDRESSES = [ - "tFS7INVALIDADDRESS00", - "tFS7INVALIDADDRESS01", - "tFS7INVALIDADDRESS02", - "tFS7INVALIDADDRESS03", - "tFS7INVALIDADDRESS04", - "tFS7INVALIDADDRESS05", - "tFS7INVALIDADDRESS06", - "tFS7INVALIDADDRESS07", - "tFS7INVALIDADDRESS08", - "tFS7INVALIDADDRESS09", - "tFS7INVALIDADDRESS10", - "tFS7INVALIDADDRESS11", - ]; - - std::vector FS_8_ADDRESSES = [ - "tFS8INVALIDADDRESS00", - "tFS8INVALIDADDRESS01", - "tFS8INVALIDADDRESS02", - "tFS8INVALIDADDRESS03", - "tFS8INVALIDADDRESS04", - "tFS8INVALIDADDRESS05", - "tFS8INVALIDADDRESS06", - "tFS8INVALIDADDRESS07", - "tFS8INVALIDADDRESS08", - "tFS8INVALIDADDRESS09", - "tFS8INVALIDADDRESS10", - "tFS8INVALIDADDRESS11", - ]; - -- To-do: specify the correct sets of FR addresses. -- To-do: require that the FR address sets are PGP-signed with appropriate keys. Example implementation ---------------------- @@ -303,14 +209,9 @@ Example implementation }; enum FundingStream { - FS_1, - FS_2, - FS_3, - FS_4, - FS_5, - FS_6, - FS_7, - FS_8, + FS_ECC, + FS_ZF, + FS_MG, MAX_FUNDING_STREAMS, }; @@ -343,14 +244,9 @@ Example implementation consensus.nFundingPeriodLength = consensus.nSubsidyPostBlossomHalvingInterval / 48; - AddZIP207FundingStream(consensus, Consensus::FS_1, FS_1_ADDRESSES, 3, 40); - AddZIP207FundingStream(consensus, Consensus::FS_2, FS_2_ADDRESSES, 1, 25); - AddZIP207FundingStream(consensus, Consensus::FS_3, FS_3_ADDRESSES, 1, 40); - AddZIP207FundingStream(consensus, Consensus::FS_4, FS_4_ADDRESSES, 1, 50); - AddZIP207FundingStream(consensus, Consensus::FS_5, FS_5_ADDRESSES, 1, 80); - AddZIP207FundingStream(consensus, Consensus::FS_6, FS_6_ADDRESSES, 1, 80); - AddZIP207FundingStream(consensus, Consensus::FS_7, FS_7_ADDRESSES, 1, 100); - AddZIP207FundingStream(consensus, Consensus::FS_8, FS_8_ADDRESSES, 1, 200); + AddZIP207FundingStream(consensus, Consensus::FS_ECC, FS_ECC_ADDRESSES, 7, 100); + AddZIP207FundingStream(consensus, Consensus::FS_ZF, FS_ZF_ADDRESSES, 5, 100); + AddZIP207FundingStream(consensus, Consensus::FS_MG, FS_MG_ADDRESSES, 8, 100); ... } @@ -406,7 +302,7 @@ Example implementation { ... - if (NetworkUpgradeActive(nHeight, consensusParams, Consensus::UPGRADE_BLOSSOM)) { + if (NetworkUpgradeActive(nHeight, consensusParams, Consensus::UPGRADE_NU4)) { // Coinbase transaction must include outputs corresponding to the consensus // funding streams active at the current block height. auto requiredStreams = GetActiveFundingStreams(nHeight, consensusParams); @@ -421,14 +317,15 @@ Example implementation } if (!requiredStreams.empty()) { - return state.DoS(100, error("%s: funding stream missing", __func__), REJECT_INVALID, "cb-funding-stream-missing"); + return state.DoS(100, error("%s: funding stream missing", __func__), + REJECT_INVALID, "cb-funding-stream-missing"); } } else { // Coinbase transaction must include an output sending 20% of - // the block reward to a founders reward script, until the last founders + // the block subsidy to a Founders' Reward script, until the last founders // reward block is reached, with exception of the genesis block. - // The last founders reward block is defined as the block just before the - // first subsidy halving block, which occurs at halving_interval + slow_start_shift + // The last Founders' Reward block is defined as the block just before the + // first subsidy halving block. if ((nHeight > 0) && (nHeight <= consensusParams.GetLastFoundersRewardBlockHeight())) { bool found = false; @@ -442,7 +339,8 @@ Example implementation } if (!found) { - return state.DoS(100, error("%s: founders reward missing", __func__), REJECT_INVALID, "cb-no-founders-reward"); + return state.DoS(100, error("%s: founders reward missing", __func__), + REJECT_INVALID, "cb-no-founders-reward"); } } } @@ -454,7 +352,7 @@ Example implementation Deployment ========== -This proposal was originally intended to be deployed with the Blossom network upgrade. [#zip-0206]_ +This proposal is intended to be deployed with ${NU4}. [#zip-0251]_ Backward compatibility @@ -466,23 +364,6 @@ upgrade their software to a compatible version within the upgrade window. Older software will treat post-upgrade blocks as invalid, and will follow any pre-upgrade branch that persists. -This proposal is designed with the explicit requirement of not altering the overall issuance schedule (based -on time), nor does it alter the proportion or timeline of the overall Founders' Reward. As a result, no users -outside of the Zerocoin Electric Coin Company and Zcash Foundation should experience any UX or economic change -outside of the upgrade due to this proposal itself. - - -Interactions with other ZIPs ----------------------------- - -[#zip-0208]_ (Shorter Block Target Spacing) specifies a change to the block target spacing. It is planned -to take effect in the Blossom network upgrade [#zip-0206]_. This ZIP was originally written to take effect -at the same time, but was Withdrawn from consideration for Blossom. - -ZIP 208 modifies the payment of the original Founders' Reward to take account of the block target spacing -change. It does this by specifying a FounderAddressAdjustedHeight function and related changes, which would -need to be revisited to take into account funding streams. - Reference Implementation ======================== @@ -494,9 +375,14 @@ References ========== .. [#RFC2119] `Key words for use in RFCs to Indicate Requirement Levels `_ -.. [#block-subsidy] `Section 7.7: Calculation of Block Subsidy and Founders' Reward. Zcash Protocol Specification, Version 2018.0-beta-33 or later [Overwinter+Sapling] `_ -.. [#continued-funding] `Continued Funding and Transparency `_ +.. [#protocol] `Zcash Protocol Specification, Version 2020.1.1 or later `_ +.. [#protocol-subsidyconcepts] `Section 3.9: Block Subsidy and Founders' Reward. Zcash Protocol Specification, Version 2020.1.1 or later `_ +.. [#protocol-constants] `Section 5.3: Constants. Zcash Protocol Specification, Version 2020.1.1 or later `_ +.. [#protocol-subsidies] `Section 7.7: Calculation of Block Subsidy and Founders' Reward. Zcash Protocol Specification, Version 2020.1.1 or later `_ +.. [#protocol-foundersreward] `Section 7.8: Payment of Founders' Reward. Zcash Protocol Specification, Version 2020.1.1 or later `_ +.. [#zip-0000] `ZIP 0: ZIP Process `_ .. [#zip-0208] `ZIP 208: Shorter Block Target Spacing `_ -.. [#original-fr-consensus-rule] `Section 7.8: Payment of Founders' Reward. Zcash Protocol Specification, Version 2018.0-beta-33 or later [Overwinter+Sapling] `_ -.. [#protocol-constants] `Section 5.3: Constants. Zcash Protocol Specification, Version 2018.0-beta-33 or later [Overwinter+Sapling] `_ -.. [#zip-0206] `ZIP 206: Blossom Network Upgrade `_ +.. [#zip-0213] `ZIP 213: Shielded Coinbase `_ +.. [#zip-0214] `ZIP 214: Consensus rules for a Zcash Development Fund `_ +.. [#zip-0251] `ZIP 251: Deployment of the ${NU4} Network Upgrade `_ +.. [#zip-1014] `ZIP 1014: Establishing a Dev Fund for ECC, ZF, and Major Grants `_