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policy.go
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policy.go
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package sign
// ParticipationMask is an interface to get the total number of candidates
// and the number of participants.
type ParticipationMask interface {
// CountEnabled returns the number of participants
CountEnabled() int
// CountTotal returns the number of candidates
CountTotal() int
}
// Policy represents a fully customizable cosigning policy deciding what
// cosigner sets are and aren't sufficient for a collective signature to be
// considered acceptable to a verifier. The Check method may inspect the set of
// participants that cosigned by invoking cosi.Mask and/or cosi.MaskBit, and may
// use any other relevant contextual information (e.g., how security-critical
// the operation relying on the collective signature is) in determining whether
// the collective signature was produced by an acceptable set of cosigners.
type Policy interface {
Check(m ParticipationMask) bool
}
// CompletePolicy is the default policy requiring that all participants have
// cosigned to make a collective signature valid.
type CompletePolicy struct {
}
// Check verifies that all participants have contributed to a collective
// signature.
func (p CompletePolicy) Check(m ParticipationMask) bool {
return m.CountEnabled() == m.CountTotal()
}
// ThresholdPolicy allows to specify a simple t-of-n policy requring that at
// least the given threshold number of participants t have cosigned to make a
// collective signature valid.
type ThresholdPolicy struct {
thold int
}
// NewThresholdPolicy returns a new ThresholdPolicy with the given threshold.
func NewThresholdPolicy(thold int) *ThresholdPolicy {
return &ThresholdPolicy{thold: thold}
}
// Check verifies that at least a threshold number of participants have
// contributed to a collective signature.
func (p ThresholdPolicy) Check(m ParticipationMask) bool {
return m.CountEnabled() >= p.thold
}