zuc: add comments

pkcs7/envelope.go

@@ -210,7 +210,7 @@ func newEnvelopedData(cipher pkcs.Cipher, content []byte, contentType asn1.Objec
 
 // AddRecipient adds a recipient to the EnvelopedData structure.
 // version 0: IssuerAndSerialNumber
-// version 1: SM2GB/T 35275-2017
+// version 1: GB/T 35275-2017
 // version 2: SubjectKeyIdentifier
 func (ed *EnvelopedData) AddRecipient(cert *smx509.Certificate, version int, encryptKeyFunc func(cert *smx509.Certificate, key []byte) ([]byte, error)) error {
 	if version < 0 || version > 2 {

zuc/eea.go

@@ -17,6 +17,9 @@ type eea struct {
 }
 
 // NewCipher create a stream cipher based on key and iv aguments.
+// The key must be 16 bytes long and iv must be 16 bytes long for zuc 128;
+// or the key must be 32 bytes long and iv must be 23 bytes long for zuc 256;
+// otherwise, an error will be returned.
 func NewCipher(key, iv []byte) (cipher.Stream, error) {
 	s, err := newZUCState(key, iv)
 	if err != nil {
@@ -28,6 +31,9 @@ func NewCipher(key, iv []byte) (cipher.Stream, error) {
 }
 
 // NewEEACipher create a stream cipher based on key, count, bearer and direction arguments according specification.
+// The key must be 16 bytes long and iv must be 16 bytes long, otherwise, an error will be returned.
+// The count is the 32-bit counter value, the bearer is the 5-bit bearer identity and the direction is the 1-bit 
+// transmission direction flag.
 func NewEEACipher(key []byte, count, bearer, direction uint32) (cipher.Stream, error) {
 	iv := make([]byte, 16)
 	byteorder.BEPutUint32(iv, count)

zuc/eia.go

@@ -71,6 +71,9 @@ func genIV4EIA(count, bearer, direction uint32) []byte {
 }
 
 // NewEIAHash create hash for zuc-128 eia, with arguments key, count, bearer and direction
+// The key must be 16 bytes long and iv must be 16 bytes long, otherwise, an error will be returned.
+// The count is the 32-bit counter value, the bearer is the 5-bit bearer identity and the direction is the 1-bit 
+// transmission direction flag.
 func NewEIAHash(key []byte, count, bearer, direction uint32) (*ZUC128Mac, error) {
 	return NewHash(key, genIV4EIA(count, bearer, direction))
 }