# Examples

Examples of POD2 use cases

## EthDos

Original in prolog https://gist.github.com/ludns/f84b379ec8c53c97b7f95630e16cc39c#file-eth_dos-pl

An EthDos Pod exposes a single custom statement with two custom deduction
rules, the inductive case and the base case.

```
statement eth_dos_distance(src: PubKey, dst: PubKey, distance: Int):
   - OR():
      - AND(attestation_pod: Pod, intermediate: PubKey, n: int):
         - eq(attetation_pod.attestation, dst)
         - eq(attetation_pod.type, SIGNATURE)
         - sum_of(distance, 1, n)
         - eth_dos_distance(src, attetation_pod.signer, n)
      - AND():
         - eq(src, dst)
         - eq(distance, 0)
```

## ZuKYC (classic)

Original using GPC https://github.com/proofcarryingdata/zukyc

Authority public keys:
- `ZOO_GOV`: PubKey, issues IDs
- `ZOO_DEEL`: PubKey, issues bank statements
Authority lists:
- `SANCTION_LIST`: Hash, Merkle Tree Root of set of sanctioned public keys
    - values: `["G2345678", "G1987654", "G1657678"]`
Date values:
- `NOW_MINUS_18Y`: Int, 18 years ago
- `NOW_MINUS_1Y`: Int, 1 year ago
- `NOW_MINUS_7D`: Int, 7 days ago

A ZuKYC Pod exposes a single custom statement with one custom deduction rule.

```
statement loan_check(receiver: PubKey):
   - OR():
      - AND(gov_id: Pod, paystub: Pod):
         - eq(gov_id.pk, receiver)
         # Not in the sanction list
         - does_not_contain(SANCTION_LIST, gov_id.pk)
         # Valid government-issued ID
         - eq(gov_id.signer, ZOO_GOV)
         - eq(gov_id.type, SIGNATURE)
         # At least 18 years old
         - lt(gov_id.date_of_birth, NOW_MINUS_18Y) # date_of_birdth is more than 18y old
         - eq(paystub.signer, ZOO_DEEL)
         - eq(paystub.type, SIGNATURE)
         - eq(paystub.ssn, gov_id.ssn)
         # At least one year of consistent employment with your current employer
         - lt(paystub.start_date, NOW_MINUS_1Y) # start_date is more than 1y old
         - gt(paystub.issue_date, NOW_MINUS_7D) # issue_date is less than 7d old
         # Annual salary is at least $20,000
         - gt(paystub.annual_salary, 20000)
```

## ZuKYC (simplified for P1)

This simplified version uses less statements but requires a very similar set of
features.

Authority lists:
- `SANCTION_LIST`: Hash, Merkle Tree Root of set of sanctioned public keys
    - values: `["G2345678", "G1987654", "G1657678"]`
Date values:
- `NOW_MINUS_18Y`: Int, 18 years ago
- `NOW_MINUS_1Y`: Int, 1 year ago

A ZuKYC Pod exposes a single custom statement with one custom deduction rule.

```
statement loan_check(receiver: string):
   - OR():
      - AND(gov_id: Pod, paystub: Pod):
         - eq(gov_id.id_number, receiver)
         # Not in the sanction list
         - does_not_contain(SANCTION_LIST, gov_id.id_number)
         # Valid government-issued ID
         - reveal(gov_id.signer)
         - eq(gov_id.type, SIGNATURE)
         # At least 18 years old
         - lt(gov_id.date_of_birth, NOW_MINUS_18Y) # date_of_birdth is more than 18y old
         - reveal(paystub.signer)
         - eq(paystub.type, SIGNATURE)
         - eq(paystub.ssn, gov_id.ssn)
         # At least one year of consistent employment with your current employer
         - lt(paystub.start_date, NOW_MINUS_1Y) # start_date is more than 1y old
```

## GreatBoy

A Good Boy Pod exposes one custom statement with one custom deduction rule.

```
statement good_boy(receiver: PubKey, good_boy_issuers: MerkleTree):
   - OR():
      - AND(pod: Pod):
         # A good boy issuer is my friend
         - eq(pod.type, SIGNATURE)
         - contains(good_boy_issuers, pod.signer)
         - eq(pod.friend, receiver)
```

A Great Boy Pod exposes (in addition to the above) one new custom statement
with one custom deduction rule.

```
statement great_boy(receiver: PubKey, good_boy_issuers: MerkleTree):
   - OR():
      - AND(friend_pod_0: Pod, friend_pod_1: Pod):
         # good boy 0 is my friend
         - eq(friend_pod_0.type, SIGNATURE)
         - good_boy(friend_pod_0.signer, good_boy_issuers)
         - eq(friend_pod_0.friend, receiver)
         # good boy 1 is my friend
         - eq(friend_pod_1.type, SIGNATURE)
         - good_boy(friend_pod_1.signer, good_boy_issuers)
         - eq(friend_pod_1.friend, receiver)
         # good boy 0 != good boy 1
         - neq(friend_pod_0.signer, friend_pod_1.signer)
```