diff --git a/cipher/ccm.go b/cipher/ccm.go
index e6d2b90..7b26132 100644
--- a/cipher/ccm.go
+++ b/cipher/ccm.go
@@ -1,3 +1,4 @@
+// Package cipher provides several extra chipher modes.
 package cipher
 
 import (
diff --git a/drbg/common.go b/drbg/common.go
index ec0673c..d674093 100644
--- a/drbg/common.go
+++ b/drbg/common.go
@@ -1,3 +1,4 @@
+// Package drbg implements Random Number Generation Using Deterministic Random Bit Generators.
 package drbg
 
 import (
diff --git a/kdf/kdf.go b/kdf/kdf.go
index fe3f076..58d4b69 100644
--- a/kdf/kdf.go
+++ b/kdf/kdf.go
@@ -1,3 +1,4 @@
+// Package kdf implements ShangMi(SM) used Key Derivation Function, compliances with GB/T 32918.4-2016 5.4.3.
 package kdf
 
 import (
diff --git a/padding/pkcs7.go b/padding/pkcs7.go
index 1a3ee62..8a1f8a0 100644
--- a/padding/pkcs7.go
+++ b/padding/pkcs7.go
@@ -1,4 +1,3 @@
-// Package padding handle padding octets at the trailing end
 package padding
 
 import (
diff --git a/padding/schemes.go b/padding/schemes.go
index 8e762e3..66c6273 100644
--- a/padding/schemes.go
+++ b/padding/schemes.go
@@ -1,3 +1,4 @@
+// Package padding implements some padding schemes for padding octets at the trailing end.
 package padding
 
 // Padding interface represents a padding scheme
diff --git a/pkcs8/pkcs8.go b/pkcs8/pkcs8.go
index 4dce5ad..1ca1f50 100644
--- a/pkcs8/pkcs8.go
+++ b/pkcs8/pkcs8.go
@@ -1,4 +1,4 @@
-// Package pkcs8 implements functions to parse and convert private keys in PKCS#8 format, as defined in RFC5208 and RFC5958
+// Package pkcs8 implements functions to parse and convert private keys in PKCS#8 format with ShangMi(SM) support, as defined in RFC5208 and RFC5958.
 package pkcs8
 
 import (
diff --git a/sm2/sm2.go b/sm2/sm2.go
index aa9024b..ff7fe7b 100644
--- a/sm2/sm2.go
+++ b/sm2/sm2.go
@@ -1,4 +1,4 @@
-// Package sm2 handle shangmi sm2 digital signature and public key encryption algorithm and its curve implementation
+// Package sm2 implements ShangMi(SM) sm2 digital signature, public key encryption and key exchange algorithms.
 package sm2
 
 // Further references:
diff --git a/sm2/sm2_test.go b/sm2/sm2_test.go
index d950ecb..7dddc6d 100644
--- a/sm2/sm2_test.go
+++ b/sm2/sm2_test.go
@@ -9,7 +9,9 @@ import (
 	"crypto/rand"
 	"encoding/hex"
 	"errors"
+	"fmt"
 	"io"
+	"log"
 	"math/big"
 	"reflect"
 	"testing"
@@ -369,6 +371,21 @@ func TestSignVerify(t *testing.T) {
 	}
 }
 
+// This is a reference method to force SM2 standard with SDK [crypto.Signer].
+func ExamplePrivateKey_Sign_forceSM2() {
+	toSign := []byte("ShangMi SM2 Sign Standard")
+	priv, _ := GenerateKey(rand.Reader)
+	// force SM2 sign standard and use default UID
+	sig, err := priv.Sign(rand.Reader, toSign, NewSM2SignerOption(true, nil))
+	if err != nil {
+		log.Fatalf("%v", err)
+	}
+	// use default UID
+	ok := VerifyASN1WithSM2(&priv.PublicKey, nil, toSign, sig)
+	fmt.Printf("%v\n", ok)
+	// Output: true
+}
+
 func TestSignVerifyLegacy(t *testing.T) {
 	priv, _ := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
 	tests := []struct {
@@ -583,30 +600,31 @@ func TestEqual(t *testing.T) {
 	}
 }
 
-// a sample method to get frist ASN1 SEQUENCE data
-func getFirstASN1Sequence(ciphertext []byte) ([]byte, []byte, error) {
-	input := cryptobyte.String(ciphertext)
-	var inner cryptobyte.String
-	if !input.ReadASN1(&inner, asn1.SEQUENCE) {
-		return nil, nil, errors.New("there are no sequence tag")
+// This method provide a sample to handle ASN1 ciphertext ends with extra bytes.
+func Example_parseCipherASN1EndsWithInvalidBytes() {
+	// a sample method to get frist ASN1 SEQUENCE data
+	getFirstASN1Sequence := func(ciphertext []byte) ([]byte, []byte, error) {
+		input := cryptobyte.String(ciphertext)
+		var inner cryptobyte.String
+		if !input.ReadASN1(&inner, asn1.SEQUENCE) {
+			return nil, nil, errors.New("there are no sequence tag")
+		}
+		if len(input) == 0 {
+			return ciphertext, nil, nil
+		}
+		return ciphertext[:len(ciphertext)-len(input)], input, nil
 	}
-	if len(input) == 0 {
-		return ciphertext, nil, nil
-	}
-	return ciphertext[:len(ciphertext)-len(input)], input, nil
-}
 
-func TestCipherASN1WithInvalidBytes(t *testing.T) {
 	ciphertext, _ := hex.DecodeString("3081980220298ED52AE2A0EBA8B7567D54DF41C5F9B310EDFA4A8E15ECCB44EDA94F9F1FC20220116BE33B0833C95D8E5FF9483CD2D7EFF7033C92FE5DEAB6197D809FF1EEE05F042097A90979A6FCEBDE883C2E07E9C286818E694EDE37C3CDAA70E4CD481BE883E00430D62160BB179CB20CE3B5ECA0F5A535BEB6E221566C78FEA92105F71BD37F3F850AD2F86F2D1E35F15E9356557DAC026A")
 	_, rest, err := getFirstASN1Sequence(ciphertext)
 	if err != nil || len(rest) != 0 {
-		t.FailNow()
+		log.Fatalf("can't get a complete ASN1 sequence")
 	}
 
 	ciphertext, _ = hex.DecodeString("3081980220298ED52AE2A0EBA8B7567D54DF41C5F9B310EDFA4A8E15ECCB44EDA94F9F1FC20220116BE33B0833C95D8E5FF9483CD2D7EFF7033C92FE5DEAB6197D809FF1EEE05F042097A90979A6FCEBDE883C2E07E9C286818E694EDE37C3CDAA70E4CD481BE883E00430D62160BB179CB20CE3B5ECA0F5A535BEB6E221566C78FEA92105F71BD37F3F850AD2F86F2D1E35F15E9356557DAC026A0000")
 	seq, rest, err := getFirstASN1Sequence(ciphertext)
 	if err != nil || len(rest) != 2 {
-		t.FailNow()
+		log.Fatalf("can't get a complete ASN1 sequence")
 	}
 
 	var (
@@ -623,7 +641,7 @@ func TestCipherASN1WithInvalidBytes(t *testing.T) {
 		!inner.ReadASN1Bytes(&c3, asn1.OCTET_STRING) ||
 		!inner.ReadASN1Bytes(&c2, asn1.OCTET_STRING) ||
 		!inner.Empty() {
-		t.Fatalf("invalid cipher text")
+		log.Fatalf("invalid cipher text")
 	}
 }
 
@@ -676,10 +694,10 @@ func TestRandomPoint(t *testing.T) {
 	}
 }
 
-// This test method is just for reference, it's NOT a standard method for key transmission.
+// This example method is just for reference, it's NOT a standard method for key transmission.
 // In general, private key will be encoded/formatted with PKCS8, public key will be encoded/formatted with a SubjectPublicKeyInfo structure
 // (see RFC 5280, Section 4.1).
-func TestCreateKeysFromRawValue(t *testing.T) {
+func Example_createKeysFromRawValue() {
 	key, _ := GenerateKey(rand.Reader)
 
 	d := new(big.Int).SetBytes(key.D.Bytes()) // here we do NOT check if the d is in (0, N) or not
@@ -689,7 +707,7 @@ func TestCreateKeysFromRawValue(t *testing.T) {
 	keyCopy.D = d
 	keyCopy.PublicKey.X, keyCopy.PublicKey.Y = keyCopy.ScalarBaseMult(keyCopy.D.Bytes())
 	if !key.Equal(keyCopy) {
-		t.Fatalf("private key and copy should be equal")
+		log.Fatalf("private key and copy should be equal")
 	}
 
 	pointBytes := elliptic.Marshal(key.Curve, key.X, key.Y)
@@ -698,7 +716,7 @@ func TestCreateKeysFromRawValue(t *testing.T) {
 	publicKeyCopy.Curve = P256()
 	publicKeyCopy.X, publicKeyCopy.Y = elliptic.Unmarshal(publicKeyCopy.Curve, pointBytes)
 	if !key.PublicKey.Equal(publicKeyCopy) {
-		t.Fatalf("public key and copy should be equal")
+		log.Fatalf("public key and copy should be equal")
 	}
 }
 
diff --git a/sm2/sm2ec/sm2ec.go b/sm2/sm2ec/sm2ec.go
index 5ab8a96..83432f7 100644
--- a/sm2/sm2ec/sm2ec.go
+++ b/sm2/sm2ec/sm2ec.go
@@ -1,3 +1,4 @@
+// Package sm2ec defines/implements SM2 curve structure.
 package sm2ec
 
 import (
diff --git a/sm3/sm3.go b/sm3/sm3.go
index 2ad99fa..10d52e8 100644
--- a/sm3/sm3.go
+++ b/sm3/sm3.go
@@ -1,4 +1,4 @@
-// Package sm3 handle shangmi sm3 hash algorithm
+// Package sm3 implements ShangMi(SM) sm3 hash algorithm.
 package sm3
 
 // [GM/T] SM3 GB/T 32905-2016
diff --git a/sm4/cipher.go b/sm4/cipher.go
index b07dc1d..29316e6 100644
--- a/sm4/cipher.go
+++ b/sm4/cipher.go
@@ -1,4 +1,4 @@
-// Package sm4 handle shangmi sm4 symmetric encryption algorithm
+// Package sm4 implements ShangMi(SM) sm4 symmetric encryption algorithm.
 package sm4
 
 import (
diff --git a/sm9/bn256/bn_pair.go b/sm9/bn256/bn_pair.go
index 0986725..51f4adb 100644
--- a/sm9/bn256/bn_pair.go
+++ b/sm9/bn256/bn_pair.go
@@ -1,3 +1,4 @@
+// Package bn256 defines/implements ShangMi(SM) sm9's curves and pairing.
 package bn256
 
 func lineFunctionAdd(r, p *twistPoint, q *curvePoint, r2 *gfP2) (a, b, c, d *gfP2, rOut *twistPoint) {
diff --git a/sm9/sm9.go b/sm9/sm9.go
index a043880..9530f76 100644
--- a/sm9/sm9.go
+++ b/sm9/sm9.go
@@ -1,4 +1,4 @@
-// Package sm9 handle shangmi sm9 algorithm and its curves and pairing implementation
+// Package sm9 implements ShangMi(SM) sm9 digital signature, encryption and key exchange algorithms.
 package sm9
 
 import (
diff --git a/zuc/core.go b/zuc/core.go
index 15359d4..4e5318c 100644
--- a/zuc/core.go
+++ b/zuc/core.go
@@ -1,4 +1,4 @@
-// Package zuc handle shangmi zuc stream cipher.
+// Package zuc implements ShangMi(SM) zuc stream cipher and integrity algorithm.
 package zuc
 
 import (