Skip to content

Commit

Permalink
HIP14: spring cleaning (#63)
Browse files Browse the repository at this point in the history
  • Loading branch information
@anthonyra
anthonyra authored Oct 22, 2020
1 parent cb2da2d commit 2b02b5c
Showing 1 changed file with 97 additions and 84 deletions.
181 changes: 97 additions & 84 deletions 0014-poc-ripple-method.md
View file
Original file line number Diff line number Diff line change
Expand Up @@ -9,136 +9,141 @@
# Summary
[summary]: #summary

The current Proof-of-Coverage allows for Virtual Machine (VM) farms or hotspot farms that have been engineered to maximize return of rewards without providing benefit to the network.
<!-- TODO: Link sections that resolve issues here !-->

The current PoC model also rewards those hotspots that are in the most dense part of the network more than the edges. Resulting in over-coverage of those areas and limited expansion to new areas.

This HIP proposes a different method to to determine Proof-of-Coverage, by seperating the network into islands that are based on the geolocation of hotspots and their associated witness lists.

![Initial Pebble Hop](https://github.com/helium/hip/blob/master/0014-poc-ripple-method/initial.png?raw=true)
The current Proof-of-Coverage (PoC) - Onion Packet method has the following issues that this proposal is meant to resolve:
1. The data used to validate coverage can be easily modified or spoofed
1. RF - RSSI, SNR
2. GPS
3. Assert Location
2. Current rewards associated to PoC is heavily favored in areas with high hotspot density (over-coverage)
1. Modesto, CA
2. New York City, NY
3. Port Huron, MI
3. The selection process even though based on randomness can be selective due to the nature of the witness list. Since a group of hotspots can be engineered or placed to only witness themselves this approach allows for isolated groups. This makes it easy to build Virtual Machine (VM) or RF based hotspot farms. [This issue will be resolved with how the Ripple Effect functions][rippleBenefits]


# Motivation
[motivation]: #motivation

With a new day comes a new way "bad actors" attempt to profit from the current system. To fully understand this proposal you first need to grasp the basics on how the current PoC system works. [PoC Documentation](https://developer.helium.com/blockchain/proof-of-coverage)

#### Basics of current PoC
*Note* If the following doesn't make sense please check out the above PoC documenation.
With a new day comes a new way "bad actors" attempt to profit from the current system. To fully understand this proposal you first need to grasp the basics of the current PoC system.

#### Basics of Current PoC
1. A challenger selects a target hotspot.
2. Once selected the challenger creates a PoC proof
1. Starting with the target hotspot the challenger selects the next hotspot in the PoC path based on witness list and [hex](https://h3geo.org/docs) location (how the 300m limit is enforced).
2. The challenger repeats the above step (2.i) but starting with the hotspot selected to be the next hop.
3. This PoC path is created containing 2 - 5 hotspots (hops)
2. The challenger repeats the above step (2.i) but starts with the hotspot selected to be the next hop.
3. The PoC path is created containing 2 - 5 hotspots (hops)
3. The initial challengee receives the PoC proof via the p2p network and decrypts the packet (envelope) it signs it and then returns it to the challenger
4. The hotspot then broadcasts the new envelope that is now one layer less than the previous one via Radio Frequency (LoRa / RF).
5. This signal is then picked up by neighboring hotspots. The receiving hotspots have two options.
1. The hotspot is the next hop in the PoC proof so it's able to decrypt another layer of the envelope and perform steps (4-5.i).
2. The hotspot isn't the next hop so it signs the envelope and returns to sender (challenger) via p2p.
6. Steps 4 - 5 continue until the end of the PoC proof is reached resulting in a PoC receipt. This PoC receipt is then sent from the challenger to the Consensus Group to be validated.

#### Current Issues:
1. Due to the targeting techinque used (witness list) it's possible for farms to create isolated islands that will be picked for PoC and perform well between the hotspots in the farm but not to others.
2. The PoC path becomes very computationally extensive to validate the more dense the network is where the PoC took place.
3. All passed challengees and witnesses (up to 5 per challengee) are currently reward for a PoC receipt. Which can result in a farm receiving 20 rewards per hotspot even though only 5 PoC challenges were issued.
For more details go to: [PoC Documentation](https://developer.helium.com/blockchain/proof-of-coverage)



# Stakeholders
[stakeholders]: #stakeholders

* If this HIP is implemented it will effect everyone who owns a hotspot due to reward changes based on PoC.
* If this HIP is implemented it will effect everyone who owns a hotspot due to reward changes based on the new PoC method.
* Feedback will be received via the Github `Issues` discussion and on [Discord #hips](https://discord.gg/helium)

# Detailed Explanation
# Detailed Explanation - Ripple PoC Method
[detailed-explanation]: #detailed-explanation

## Ripple PoC Method

The network will be seperated into islands that are based on the geolocation of hotspots and their associated witness lists.

The size of an island will be limited to the following:
* The smallest an island can be one hex
* The largest an island would be 7 hexs

The above size constraints are due to the max chain count that occurs with the `ripple` method which will be described in more detail below.


#### Definitions
[definitions]: #definitions

* `Island` - A hex-cluster that is created by the island construction method below which visualizes the coverage of an area
* `Island Hex` - The hex used to create the island. It'll be of resolution 8 (~415m [0.25 miles] sides, ~0.447454km2 [110 acres] total area)
* `Children Hex` - The hex's found inside of the `Island Hex` of resolution 12 linked via hotspot location hex
* `Island Rating` - The overall rating of an island
* `Island` - A hex-cluster that is created by the island construction method below which visualizes the coverage of an area.
* `Island Hex` - The hex used to create the island ( h3 resolution 8 hex: ~0.45km2 [110 acres] )
* `Hotspot Hex` - The hex associate with hotspot location currently in the blockchain
* `Island Rating` - The overall rating of an island based on total # of chains received and longest chain in meters
* `Challenger` - The hotspot that selects the `Island` to be targeted and the `Pebble` hotspots for the challenge
* `Pebble (challengee)` - Selected by the challenger to start the *ripple*. Minimum of 2 all must be in a different `Island Hex`
* `Accpeted Chain` - Chain that starts with a `Pebble` and ends with a `Pebble` hotspot with all hotspots signatures for each hop

| Accepted Chains |
| --- | --- |
| pHi - pHo |
| pHi - iH - pHi |
| pHi - iH1 ... iHn - pHo |

```
pHi (blue) = initial pebble hotspot
pHo (orange) = opposite pebble hotspot
iH (green) = island hotspot
iHx (grey) = island hex
```

* `Witness List` - Will be generated from the `pHi - iH - pHi` chains. This list won't incorporate hotspots within the same `Island Hex` but is included in the PoC due to the island construction
* `Pebble (challengee)` - Selected by the challenger to start the *ripple*. There are two types of pebbles, the `initial` and `opposite`. The initial pebble receives the packet from challenger and the opposite pebble is the *target* for that packet. Each must be in a different `Island Hex`
* `Accpeted Chain` - A chain that starts with a `Pebble` and ends with a `Pebble` hotspot with all hotspots signatures for each hop

| Accepted Chains |
| :-: |
| pHi => pHo |
| pHi => iH => pHi |
| pHi => iH1 ... iHn => pHo |
| |
| pHi (blue) = Initial Pebble Hotspot <br /> pHo (orange) = Opposite Pebble Hotspot <br /> iH (green) = Island Hotspot |

* `Witness List` - Will be generated from the `pHi => iH => pHi` chains. This list won't incorporate hotspots within the same `Island Hex` but is included in the PoC due to the island construction
* `Cave` - A cluster of hotspots that are isolated from the rest of the island


#### Island Construction
[islandConstruction]: #islandConstruction

The network will be seperated into islands that are based on the geolocation of hotspots and their associated witness lists initially. Once the network is divided into Islands any new hotspots will just be added to existing [`Island`][definitions]. If the hotspot is added to a location without a current `Island` or the `Island` is less than 7 hexs in size. The original founder (hotspot) for that `Island` will expand the `Island` based on it's witness list.

1. The oldest hotspot based on block age will start the first island
2. The witnesses of that hotspot will be ranked based on block age
3. The oldest witness with a different `Island Hex` will select the next `Island Hex` for the island
4. Steps 2 - 3 will repeat until the max `Island` size of 7 is reached or no more witnesses exist
5. The next oldest hotspot is then selected and either added to an existing island or creates a new one repeating steps 2 - 4 above.
6. This is performed until all hotspots have an associated `Island` and `Island Hex`

Currently the island is constructed by selecting a random hotspot and based on it's associated hex will commence the construction of the island.
<!-- Still working on converting current network to Islands for this data
1. A random hotspot is selected
2. The hotspot's location hex string is selected
3. The island hex is found by expanding the location hex (resolution 12) to the island hex (resolution 8)
4. The island hex (resolution 8) is used to find all children hex (resolution 12)
5. The hotspots that are located in one of the children hex is add to the list of hotspots for the island
6. The list of hotspots is looped to get all witnesses to those hotspots
7. Step 2 - 5 are repeated for all witness hotspots
8. Once there are no more witness found the process ends
<p align="center">
🚧 Data was collected on 10/21/2020 - Network Size: 10,510 🚧
</p>
*The above process is only for proof of concept*
| Size | # |
| :--: | :-: |
| 1 | 80 <br /> 🐺 3716 |
| 2 | 614 |
| 3 | 307 |
| 4 | 154 |
| 5 | 102 |
| 6 | 62 |
| 7 | 356 |
Ideally if adopted for this to be efficient as possible when a hotspot performs an `assert_location` transaction it will not only be assigned a location but also an island hex.
This will greatly speed up the process since there wouldn't need to be a re-index of hotspots to island hexs.
🐺 are Islands that only consist of one hex with one hotspot in them and no witnesses
#### Ripple Effect
!-->
## Ripple Effect
[rippleEffect]: #rippleEffect

Once an `Island` is created for an area the `Challenger` will be able to perform the `ripple` method of PoC on that `Island`.
1. The [`Challenger`][definitions] selects the [`Island`][definitions] to be challenged
2. Then it selects the [`Pebble`][definitions] hotspots within that `Island`
3. Once the `Pebble` hotspots are selected, the `Challenger` will initiate the `ripple`. The packet being sent will have the challenger information and the expected hexs that packet will pass through to reach maximum chain length. Only the opposite `Pebble` of the pair can decrypt the packet received to then send back to challenger or Consensus Group
4. The `Pebble` hotspots receive the packet
1. They sign the packet in the spot for their [`Island Hex`][definitions] and broadcast it via RF (LoRa)
5. There are two options for the hotspots that receive this broadcasted packet
1. If, the receiving hotspot is the opposite `Pebble` hotspot, in this case the envelope will be able to be decrypted and sent back to the challenger
2. If, the receiving hotspot is **not** the opposite `Pebble` hotspot it will perform step (4.i) above
6. This "ripple" occurs for a set timeframe or when the `Challenger` receives the expected number of chains from the `Pebble` hotspots

1. The `Challenger` will select the island it'll be challenging
2. Once the `Island` is selected the `Challenger` will select the `Pebble` hotspots
3. The `Challenger` will send the packet it created to the `Pebble` hotspots. Only the opposite `Pebble` of the pair can decrypt the packet received
4. The `Pebble` hotspots receive the envelope
1. They sign the envelope with their `Island Hex` and broadcast it via RF (LoRa)
5. There are two options for the hotspots that receive that broadcasted envelope
1. The receiving hotspot is the opposite `Pebble` hotspot, in this case the envelope will be able to be decrypted and sent back to the challenger
2. The receiving hotspot is **not** the opposite `Pebble` hotspot, in this case it performs step (4.i)
6. This `ripple` occurs for a set timeframe or when the `Challenger` receives the expected number of chains from the `Pebble` hotspots
##### Chain Limitations
[chainLimitation]: #chainLimitation

##### Limitations
To simplify the process and lower the packets (envelopes) "broadcast storm" that the island experiences due to the `ripple` the following limitation will be set.

To simplify the process and lower the packets (envelopes) received due to the `ripple` the following limitation is set.
1. Based on the island there will be only `N` number of hexs that the packet can travel. Because of this the packet will have `N` number of segments that can only be signed by a hotspot that is found in that `Island Hex`.
2. If the packet is received by a hotspot in a hex, where the hex has already been signed for by a different hotspot the packet would be dropped.
3. The hotspot records all the chains that it's seen. If the hotspot receives a packet from a chain it's already has seen it drops that packet.

* If the hotspot receives an envelope that has been signed by it's island hex or an island hex it's already seen it's dropped. Forcing the packet to move outwards to the rest of the hex's in the `Island`
An example for limitation 3 above, if the hotspot has seen and signed a packet with the following chain `pHo => iH1` it will then drop all following packets that have that same chain. Since it's possible for multiple hotspots to reside in the same hex. This limitation is meant to limit the size of the "broadcast storm" but if it's determined that it wouldn't be that constraining this could be removed.

##### Benefits
1. Only the challenger will know which `Pebble` hotspots were selected
2. Based on the size constraint and the fact that the `Chain` is terminated if it returns to an already signed `Island Hex` results in a max number of possible ` Accepted Chains` with a max `Chain` length
3. Since it's assumed that all hotspots within an `Island` are able to communicate due to the size of the `Island Hex` and associated witness lists. Any seperation in the `ripple` and `ideal ripple` will indicate the presense of isolated hotspot(s) `Cave`.
[rippleBenefits]: #rippleBenefits

Caves will be quite obvious with the `ripple` method
1. Only the challenger will know which `Pebble` hotspots were selected
2. Based on the island size constraint and the fact that the chain is terminated based on the above [`Chain Limitations`][chainLimitation] results in a max number of possible [`Accepted Chains`][definitions] with a specific max chain length
3. Since it's assumed that all hotspots within an `Island` are able to communicate due to the size of the `Island Hex` and associated witness lists. Any seperation in the `ripple` and `ideal ripple` will indicate the presense of an isolated hotspot(s) a `Cave`.

#### Validation Process

The validation comes from the fact that the `Pebble` hotspots will create the same number of chains and lengths as each other. The difference how ever is that the chains will be mirror copies of each other.

This is of course based on ideal conditions and an ideal `Island`, in fact there will be differences between the ideal and real results. This will result in the `Island Rating`. The closer the `ripple` of a challenge gets to the `ideal ripple` the higher the rating.
This is of course based on ideal conditions and an ideal `Island`, in fact there will be differences between the ideal and real results. Because of these difference an `Island Rating` will be implemented. The closer the `ripple` of a challenge gets to the `ideal ripple` the higher the rating.

`Island Rating` Factors:
* Did the `ripple` create the max number of chains
Expand All @@ -148,7 +153,7 @@ This is of course based on ideal conditions and an ideal `Island`, in fact there
(# of chains received / Max # of Chains) + (Longest Chain / Longest Chain That Block) = 2
```

Therefore, to receive the max rating the island needs to be spread out far enough in attempt to be the longest chain per that block. When this occurs it increases the chance of hotspots that originally weren't in the selected hotspots witness list to be incorporated in the PoC of the island.
Therefore, to receive the max rating the `Island` needs to be spread out far enough in attempt to be the longest chain per that block. When this occurs it increases the chances of hotspots that originally weren't in the selected hotspots witness list to be incorporated in the PoC of the island.

The `Island` than needs to ensure the max number of chains is received by the `Target` hotspot with all hops signed by the associated hotspot.

Expand All @@ -162,7 +167,7 @@ Figure 1-1 - Initial pebble hop

![Longest Chain Example](https://github.com/helium/hip/blob/master/0014-poc-ripple-method/longest-chain-example-tall.png?raw=true)

Figure 1-1 - Example of a Longest Chain, which results in a total 6 accepted chains
Figure 1-1 - Example of a Longest Chain, which results in a total of 6 accepted chains

```
pH (blue) = pebble hotspot
Expand All @@ -175,7 +180,7 @@ Longest Chain (length) = (# of iHx - # of pH) => (7 - 2) = 5
Max Number of Longest Chain = # of iH = 5
```

With the above equations, you can calculate the max number of chains and assocaited lengths. For a 7 hex island the resulting `ripple` would have 240 different chains that are 5 hex's in length.
With the above equations, you can calculate the max number of chains and associated lengths. For a 7 hex island the resulting `ripple` would have 240 different chains that are 5 hex's in length.

#### Real Life Examples

Expand Down Expand Up @@ -231,6 +236,12 @@ Small Island Rating = (240 / 240) + ( 100m / 14000m ) = 1.007142857142857
2. (3.3491 HNT) / ( 240 ) = 0.014 HNT per hotspot
```

## Bounties

#### Island Bounties
With the rewards structured to payout to the `Island` you're able to provide the ability for external sources to added additional funds to that `Island` to incentives it's growth.


# Drawbacks
[drawbacks]: #drawbacks

Expand All @@ -243,6 +254,8 @@ Small Island Rating = (240 / 240) + ( 100m / 14000m ) = 1.007142857142857

This is a drastic change to the current Proof-of-Coverage model. It will require extensive review and testing.

HIP15 combined with HIP17 are alternatives to this proposal keeping to a lot of the same mechinisms that are in place.

# Unresolved Questions
[unresolved]: #unresolved-questions

Expand Down

0 comments on commit 2b02b5c

Please sign in to comment.