Changes based on PR comments

blsSignatures/blsSignatures.go

@@ -217,6 +217,10 @@ func PublicKeyFromBytes(in []byte, trustedSource bool) (PublicKey, error) {
 		if !trustedSource {
 			return PublicKey{}, errors.New("tried to deserialize unvalidated public key from untrusted source")
 		}
+		// The most significant bit, when set, indicates that the point is in compressed form. Otherwise, the point is in uncompressed form.
+		if (in[1] & (1 << 7)) != 0 {
+			return PublicKey{}, errors.New("invalid serialized public key")
+		}
 		err := key.Unmarshal(in[1:])
 		if err != nil {
 			return PublicKey{}, err
@@ -228,11 +232,19 @@ func PublicKeyFromBytes(in []byte, trustedSource bool) (PublicKey, error) {
 		}
 		validityProof := new(bls12381.G1Affine)
 		proofBytes := in[1 : 1+proofLen]
+		// The most significant bit, when set, indicates that the point is in compressed form. Otherwise, the point is in uncompressed form.
+		if (proofBytes[0] & (1 << 7)) != 0 {
+			return PublicKey{}, errors.New("invalid serialized validity proof")
+		}
 		err := validityProof.Unmarshal(proofBytes)
 		if err != nil {
 			return PublicKey{}, err
 		}
 		keyBytes := in[1+proofLen:]
+		// The most significant bit, when set, indicates that the point is in compressed form. Otherwise, the point is in uncompressed form.
+		if (keyBytes[0] & (1 << 7)) != 0 {
+			return PublicKey{}, errors.New("invalid serialized public key")
+		}
 		err = key.Unmarshal(keyBytes)
 		if err != nil {
 			return PublicKey{}, err
@@ -260,6 +272,10 @@ func SignatureToBytes(sig Signature) []byte {
 }
 
 func SignatureFromBytes(in []byte) (Signature, error) {
+	// The most significant bit, when set, indicates that the point is in compressed form. Otherwise, the point is in uncompressed form.
+	if (in[0] & (1 << 7)) != 0 {
+		return nil, errors.New("invalid serialized signature")
+	}
 	g1 := new(bls12381.G1Affine)
 	err := g1.Unmarshal(in)
 	if err != nil {