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backend.go
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backend.go
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// Copyright 2021 PolyCrypt GmbH
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package channel
import (
"fmt"
"log"
eth "github.com/ethereum/go-ethereum/crypto"
pchannel "perun.network/go-perun/channel"
pwallet "perun.network/go-perun/wallet"
)
// backend implements the backend interface.
// The type is private since it only needs to be exposed as singleton by the
// `Backend` variable.
type backend struct{}
// Backend is the channel backend. Is a singleton since there is only one backend.
var Backend backend
// CalcID calculates the channelID.
func (*backend) CalcID(params *pchannel.Params) (id pchannel.ID) {
return CalcID(params)
}
// Sign signs a state with the passed account.
func (*backend) Sign(acc pwallet.Account, state *pchannel.State) (pwallet.Sig, error) {
_state, err := NewState(state)
if err != nil {
return nil, err
}
data, err := ScaleEncode(_state)
if err != nil {
return nil, err
}
return acc.SignData(data)
}
// Verify verifies a signature on a state.
func (*backend) Verify(addr pwallet.Address, state *pchannel.State, sig pwallet.Sig) (bool, error) {
_state, err := NewState(state)
if err != nil {
return false, err
}
data, err := ScaleEncode(_state)
if err != nil {
return false, err
}
return pwallet.VerifySignature(data, sig, addr)
}
// NewAsset returns a variable of type Asset, which can be used
// for unmarshalling an asset from its binary representation.
func (*backend) NewAsset() pchannel.Asset {
return Asset
}
// CalcID calculates the channelID by encoding and hashing the params.
func CalcID(params *pchannel.Params) (id pchannel.ID) {
_params, err := NewParams(params)
if err != nil {
panic(fmt.Sprintf("cannot calculate channel ID: %v", err))
}
bytes, err := ScaleEncode(_params)
if err != nil {
log.Panicf("could not encode parameters: %v", err)
}
return eth.Keccak256Hash(bytes)
}