Merge pull request #704 from gregdhill/chore/sovereign-accounts

chore: document sovereign account calculation

docs/sovereign_accounts.md

@@ -0,0 +1,82 @@
+# Sovereign Accounts
+
+The trait `AccountIdConversion` is implemented for all `Id: TypeId`. Accounts are generated using [this method](https://github.com/paritytech/substrate/blob/7266eb7d794d74a7860fe193d7a3074200765ea1/primitives/runtime/src/traits.rs#L1707-L1711) and converted [here](https://github.com/paritytech/polkadot/blob/1903e3d8ed431f7ef557af5c41bbc12f8aaa4f5e/xcm/xcm-builder/src/location_conversion.rs#L73) on the relay chain and [here](https://github.com/paritytech/polkadot/blob/1903e3d8ed431f7ef557af5c41bbc12f8aaa4f5e/xcm/xcm-builder/src/location_conversion.rs#L94) on sibling parachains.
+
+## Parent
+
+The [`TYPE_ID`](https://github.com/paritytech/polkadot/blob/1903e3d8ed431f7ef557af5c41bbc12f8aaa4f5e/parachain/src/primitives.rs#L144) is always `b"para"`. 
+
+To calculate the sovereign account on the relay chain:
+
+`b"para" = 0x70617261` + `hex(paraId)` + trailing `00` to make it 32 bytes
+
+```rust
+let mut account_id = b"para".to_vec();
+account_id.extend(&1000u16.to_le_bytes()[..]);
+account_id.resize(32, 0);
+println!("{:?}", hex::encode(account_id));
+```
+
+### Kintsugi
+
+`0x70617261` (para) + `2c08` (2092) + `0000000000000000000000000000000000000000000000000000`
+
+> `5Ec4AhNv5VHwnnfJk1AWA3UtfV2oMeN1HDYmaSDPEd3nyXW4`
+
+```shell
+> subkey inspect --public 706172612c080000000000000000000000000000000000000000000000000000 -n kusama
+Network ID/Version: kusama
+  Public key (hex):   0x706172612c080000000000000000000000000000000000000000000000000000
+  Account ID:         0x706172612c080000000000000000000000000000000000000000000000000000
+  Public key (SS58):  F7fq1inhrJsYSUkWhyZ3zqtp5K3AKBBjbPWy6VLiRGHipPi
+  SS58 Address:       F7fq1inhrJsYSUkWhyZ3zqtp5K3AKBBjbPWy6VLiRGHipPi
+```
+
+### Interlay
+
+`0x70617261` (para) + `f007` (2032) + `0000000000000000000000000000000000000000000000000000`
+
+> `5Ec4AhPbMHQn55fjyQCTm5UHAzjSgtBFWBuieCK2DwbDqGSG`
+
+```shell
+> subkey inspect --public 70617261f0070000000000000000000000000000000000000000000000000000 -n polkadot
+Network ID/Version: polkadot
+  Public key (hex):   0x70617261f0070000000000000000000000000000000000000000000000000000
+  Account ID:         0x70617261f0070000000000000000000000000000000000000000000000000000
+  Public key (SS58):  13YMK2efD4gFWcgFw3FTuEJS2cj6PBjPageCoVJNn2ck1uz4
+  SS58 Address:       13YMK2efD4gFWcgFw3FTuEJS2cj6PBjPageCoVJNn2ck1uz4
+```
+
+## Sibling
+
+The [`TYPE_ID`](https://github.com/paritytech/polkadot/blob/1903e3d8ed431f7ef557af5c41bbc12f8aaa4f5e/parachain/src/primitives.rs#L256) is always `b"sibl"`. 
+
+To calculate the sovereign account on a sibling parachain:
+
+`b"sibl" = 0x7369626c` + `hex(paraId)` + trailing `00` to make it 32 bytes
+
+### Kintsugi
+
+`0x7369626c` (sibl) + `2c08` (2092) + `0000000000000000000000000000000000000000000000000000`
+
+```shell
+> subkey inspect --public 7369626c2c080000000000000000000000000000000000000000000000000000
+Network ID/Version: substrate
+  Public key (hex):   0x7369626c2c080000000000000000000000000000000000000000000000000000
+  Account ID:         0x7369626c2c080000000000000000000000000000000000000000000000000000
+  Public key (SS58):  5Eg2fnsjADUqvPPTJ17bGgphuxi754R7LsCCqPjt7M5MqVKB
+  SS58 Address:       5Eg2fnsjADUqvPPTJ17bGgphuxi754R7LsCCqPjt7M5MqVKB
+```
+
+### Interlay
+
+`0x7369626c` (sibl) + `f007` (2032) + `0000000000000000000000000000000000000000000000000000`
+
+```shell
+> subkey inspect --public 7369626cf0070000000000000000000000000000000000000000000000000000
+Network ID/Version: substrate
+  Public key (hex):   0x7369626cf0070000000000000000000000000000000000000000000000000000
+  Account ID:         0x7369626cf0070000000000000000000000000000000000000000000000000000
+  Public key (SS58):  5Eg2fntQS1bgCgPtXQ9Ysip6RUQkQJEMZqZ9u9qX6fcnhB4H
+  SS58 Address:       5Eg2fntQS1bgCgPtXQ9Ysip6RUQkQJEMZqZ9u9qX6fcnhB4H
+```