perf: use inverse as a bijection for bw6-761 mimc

Consensys · Dec 2, 2023 · f229677 · f229677
1 parent e773088
commit f229677
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Showing 2 changed files with 16 additions and 6 deletions.
diff --git a/ecc/bw6-761/fr/mimc/mimc.go b/ecc/bw6-761/fr/mimc/mimc.go
diff --git a/internal/generator/crypto/hash/mimc/template/mimc.go.tmpl b/internal/generator/crypto/hash/mimc/template/mimc.go.tmpl
@@ -177,6 +177,20 @@ func (d *digest) encrypt(m fr.Element) fr.Element {
 	m.Add(&m, &d.h)
 	return m
 }
+{{ else if eq .Name "bw6-761" }}
+// plain execution of a mimc run
+// m: message
+// k: encryption key
+func (d *digest) encrypt(m fr.Element) fr.Element {
+	once.Do(initConstants) // init constants
+
+	for i := 0; i < mimcNbRounds; i++ {
+		// m = 1/(m+k+c)
+		m.Add(&m, &d.h).Add(&m, &mimcConstants[i]).Inverse(&m)
+	}
+	m.Add(&m, &d.h)
+	return m
+}
 {{ else }}
 // plain execution of a mimc run
 // m: message