From 5d6df51d96f29e1188cb7a4a8bec06a9d970484b Mon Sep 17 00:00:00 2001
From: Sergey Matveev <stargrave@stargrave.org>
Date: Fri, 19 Jun 2020 15:58:30 +0300
Subject: [PATCH] PrivateKeyReverseDigest and
 PrivateKeyReverseDigestAndSignature

---
 VERSION             |  2 +-
 gost3410/private.go | 35 +++++++++++++++++++++++++++++++++++
 install.texi        |  2 +-
 news.texi           |  6 ++++++
 4 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/VERSION b/VERSION
index f2c6cb6..cf78d5b 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-4.2.3
+4.2.4
diff --git a/gost3410/private.go b/gost3410/private.go
index ae54424..645881b 100644
--- a/gost3410/private.go
+++ b/gost3410/private.go
@@ -119,3 +119,38 @@ func (prv *PrivateKey) Public() crypto.PublicKey {
 	}
 	return pub
 }
+
+type PrivateKeyReverseDigest struct {
+	Prv *PrivateKey
+}
+
+func (prv *PrivateKeyReverseDigest) Public() crypto.PublicKey {
+	return prv.Prv.Public()
+}
+
+func (prv *PrivateKeyReverseDigest) Sign(rand io.Reader, digest []byte, opts crypto.SignerOpts) ([]byte, error) {
+	d := make([]byte, len(digest))
+	copy(d, digest)
+	reverse(d)
+	return prv.Prv.Sign(rand, d, opts)
+}
+
+type PrivateKeyReverseDigestAndSignature struct {
+	Prv *PrivateKey
+}
+
+func (prv *PrivateKeyReverseDigestAndSignature) Public() crypto.PublicKey {
+	return prv.Prv.Public()
+}
+
+func (prv *PrivateKeyReverseDigestAndSignature) Sign(rand io.Reader, digest []byte, opts crypto.SignerOpts) ([]byte, error) {
+	d := make([]byte, len(digest))
+	copy(d, digest)
+	reverse(d)
+	sign, err := prv.Prv.Sign(rand, d, opts)
+	if err != nil {
+		return sign, err
+	}
+	reverse(sign)
+	return sign, err
+}
diff --git a/install.texi b/install.texi
index 441c9a1..9ce6459 100644
--- a/install.texi
+++ b/install.texi
@@ -1,7 +1,7 @@
 @node Download
 @unnumbered Download
 
-@set VERSION 4.2.3
+@set VERSION 4.2.4
 
 Preferable way is to download tarball with the signature from
 website and, for example, run tests with benchmarks:
diff --git a/news.texi b/news.texi
index d2d1e82..7d139e1 100644
--- a/news.texi
+++ b/news.texi
@@ -3,6 +3,12 @@
 
 @table @strong
 
+@anchor{Release 4.2.4}
+@item 4.2.4
+    @code{gost3410.PrivateKeyReverseDigest} reversed digests and
+    @code{PrivateKeyReverseDigestAndSignature} with also reversed signatures
+    signers appeared for convenience.
+
 @anchor{Release 4.2.3}
 @item 4.2.3
     Panic on all possible hash @code{Write} errors.
-- 
2.44.0