ADR-28 derive address functions (#9088)

* update Derive functions

* update adr-028

* changelog update

* Apply suggestions from code review

Co-authored-by: Marie Gauthier <marie.gauthier63@gmail.com>

* review updates

* remove DeriveMulti and rollback some changes in CHANGELOG

* add noop error check

Co-authored-by: Marie Gauthier <marie.gauthier63@gmail.com>

CHANGELOG.md

@@ -42,6 +42,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * [\#8786](https://github.com/cosmos/cosmos-sdk/pull/8786) Enabled secp256r1 in x/auth.
 * (rosetta) [\#8729](https://github.com/cosmos/cosmos-sdk/pull/8729) Data API fully supports balance tracking. Construction API can now construct any message supported by the application.
 * [\#8754](https://github.com/cosmos/cosmos-sdk/pull/8875) Added support for reverse iteration to pagination.
+* [#9088](https://github.com/cosmos/cosmos-sdk/pull/9088) Added implementation to ADR-28 Derived Addresses.
 
 ### Client Breaking Changes
 * [\#8363](https://github.com/cosmos/cosmos-sdk/pull/8363) Addresses no longer have a fixed 20-byte length. From the SDK modules' point of view, any 1-255 bytes-long byte array is a valid address.
@@ -82,6 +83,8 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (x/bank) [\#8798](https://github.com/cosmos/cosmos-sdk/pull/8798) `GetTotalSupply` is removed in favour of `GetPaginatedTotalSupply`
 * (x/bank/types) [\#9061](https://github.com/cosmos/cosmos-sdk/pull/9061) `AddressFromBalancesStore` now returns an error for invalid key instead of panic.
 
+
+
 ### State Machine Breaking
 
 * (x/{bank,distrib,gov,slashing,staking}) [\#8363](https://github.com/cosmos/cosmos-sdk/issues/8363) Store keys have been modified to allow for variable-length addresses.

docs/architecture/adr-028-public-key-addresses.md

@@ -135,7 +135,7 @@ type Addressable interface {
     Address() []byte
 }
 
-func NewComposed(typ string, subaccounts []Addressable) []byte {
+func Composed(typ string, subaccounts []Addressable) []byte {
     addresses = map(subaccounts, \a -> LengthPrefix(a.Address()))
     addresses = sort(addresses)
     return address.Hash(typ, addresses[0] + ... + addresses[n])
@@ -175,7 +175,7 @@ func (multisig PubKey) Address() {
   prefix := fmt.Sprintf("%s/%d", proto.MessageName(multisig), multisig.Threshold)
 
   // use the Composed function defined above
-  return address.NewComposed(prefix, keys)
+  return address.Composed(prefix, keys)
 }
 ```
 
@@ -185,14 +185,14 @@ NOTE: this section is not finalize and it's in active discussion.
 
 In Basic Address section we defined a module account address as:
 
-```
+```go
 address.Hash("module", moduleName)
 ```
 
 We use `"module"` as a schema type for all module derived addresses. Module accounts can have sub accounts. The derivation process has a defined order: module name, submodule key, subsubmodule key.
 Module account addresses are heavily used in the SDK so it makes sense to optimize the derivation process: instead of using of using `LengthPrefix` for the module name, we use a null byte (`'\x00'`) as a separator. This works, because null byte is not a part of a valid module name.
 
-```
+```go
 func Module(moduleName string, key []byte) []byte{
 	return Hash("module", []byte(moduleName) + 0 + key)
 }
@@ -208,24 +208,24 @@ If we want to create an address for a module account depending on more than one
 btcAtomAMM := address.Module("amm", btc.Addrress() + atom.Address()})
 ```
 
-We can continue the derivation process and can create an address for a submodule account.
+#### Derived Addresses
 
-```
-func Submodule(address []byte, derivationKey []byte) {
-    return Hash("module", address + derivationKey)
+We must be able to cryptographically derive one address from another one. The derivation process must guarantee hash properties, hence we use the already defined `Hash` function:
+
+```go
+func Derive(address []byte, derivationKey []byte) []byte {
+    return Hash(addres, derivationKey)
 }
 ```
 
-NOTE: if `address` is not a hash based address (with `LEN` length) then we should use `LengthPrefix`. An alternative would be to use one `Module` function, which takes a slice of keys and mapped with `LengthPrefix`. For final version we need to validate what's the most common use.
-
+Note: `Module` is a special case of the more general _derived_ address, where we set the `"module"` string for the _from address_.
 
 **Example**  For a cosmwasm smart-contract address we could use the following construction:
 ```
-smartContractAddr := Submodule(Module("cosmwasm", smartContractsNamespace), smartContractKey)
+smartContractAddr := Derived(Module("cosmwasm", smartContractsNamespace), []{smartContractKey})
 ```
 
 
-
 ### Schema Types
 
 A `typ` parameter used in `Hash` function SHOULD be unique for each account type.

types/address/hash.go

@@ -20,20 +20,21 @@ type Addressable interface {
 // Hash creates a new address from address type and key
 func Hash(typ string, key []byte) []byte {
 	hasher := sha256.New()
-	hasher.Write(conv.UnsafeStrToBytes(typ))
+	_, err := hasher.Write(conv.UnsafeStrToBytes(typ))
+	// the error always nil, it's here only to satisfy the io.Writer interface
+	errors.AssertNil(err)
 	th := hasher.Sum(nil)
 
 	hasher.Reset()
-	_, err := hasher.Write(th)
-	// the error always nil, it's here only to satisfy the io.Writer interface
+	_, err = hasher.Write(th)
 	errors.AssertNil(err)
 	_, err = hasher.Write(key)
 	errors.AssertNil(err)
 	return hasher.Sum(nil)
 }
 
-// NewComposed creates a new address based on sub addresses.
-func NewComposed(typ string, subAddresses []Addressable) ([]byte, error) {
+// Compose creates a new address based on sub addresses.
+func Compose(typ string, subAddresses []Addressable) ([]byte, error) {
 	as := make([][]byte, len(subAddresses))
 	totalLen := 0
 	var err error
@@ -62,3 +63,8 @@ func Module(moduleName string, key []byte) []byte {
 	mKey := append([]byte(moduleName), 0)
 	return Hash("module", append(mKey, key...))
 }
+
+// Derive derives a new address from the main `address` and a derivation `key`.
+func Derive(address []byte, key []byte) []byte {
+	return Hash(conv.UnsafeBytesToStr(address), key)
+}

types/address/hash_test.go

@@ -34,7 +34,7 @@ func (suite *AddressSuite) TestComposed() {
 	a2 := addrMock{[]byte{21, 22}}
 
 	typ := "multisig"
-	ac, err := NewComposed(typ, []Addressable{a1, a2})
+	ac, err := Compose(typ, []Addressable{a1, a2})
 	assert.NoError(err)
 	assert.Len(ac, Len)
 
@@ -45,18 +45,18 @@ func (suite *AddressSuite) TestComposed() {
 	assert.Equal(ac, ac2, "NewComposed works correctly")
 
 	// changing order of addresses shouldn't impact a composed address
-	ac2, err = NewComposed(typ, []Addressable{a2, a1})
+	ac2, err = Compose(typ, []Addressable{a2, a1})
 	assert.NoError(err)
 	assert.Len(ac2, Len)
 	assert.Equal(ac, ac2, "NewComposed is not sensitive for order")
 
 	// changing a type should change composed address
-	ac2, err = NewComposed(typ+"other", []Addressable{a2, a1})
+	ac2, err = Compose(typ+"other", []Addressable{a2, a1})
 	assert.NoError(err)
 	assert.NotEqual(ac, ac2, "NewComposed must be sensitive to type")
 
 	// changing order of addresses shouldn't impact a composed address
-	ac2, err = NewComposed(typ, []Addressable{a1, addrMock{make([]byte, 300, 300)}})
+	ac2, err = Compose(typ, []Addressable{a1, addrMock{make([]byte, 300, 300)}})
 	assert.Error(err)
 	assert.Contains(err.Error(), "should be max 255 bytes, got 300")
 }
@@ -75,6 +75,21 @@ func (suite *AddressSuite) TestModule() {
 	assert.NotEqual(addr2, addr3, "changing key must change address")
 }
 
+func (suite *AddressSuite) TestDerive() {
+	assert := suite.Assert()
+	var addr, key1, key2 = []byte{1, 2}, []byte{3, 4}, []byte{1, 2}
+	d1 := Derive(addr, key1)
+	d2 := Derive(addr, key2)
+	d3 := Derive(key1, key2)
+	assert.Len(d1, Len)
+	assert.Len(d2, Len)
+	assert.Len(d3, Len)
+
+	assert.NotEqual(d1, d2)
+	assert.NotEqual(d1, d3)
+	assert.NotEqual(d2, d3)
+}
+
 type addrMock struct {
 	Addr []byte
 }