diff --git a/sm2/src/pke.rs b/sm2/src/pke.rs
index 1f595648..61875511 100644
--- a/sm2/src/pke.rs
+++ b/sm2/src/pke.rs
@@ -28,11 +28,11 @@
 //! let decrypting_key = DecryptingKey::new_with_mode(secret_key.to_nonzero_scalar(), Mode::C1C2C3);
 //! assert_eq!(decrypting_key.decrypt(&ciphertext)?, plaintext);
 //!
-//! // Encrypting asn.1
-//! let ciphertext = encrypting_key.encrypt_asna1(plaintext)?;
+//! // Encrypting ASN.1 DER
+//! let ciphertext = encrypting_key.encrypt_der(plaintext)?;
 //!
-//! // Decrypting asn.1
-//! assert_eq!(decrypting_key.decrypt_asna1(&ciphertext)?, plaintext);
+//! // Decrypting ASN.1 DER
+//! assert_eq!(decrypting_key.decrypt_der(&ciphertext)?, plaintext);
 //!
 //! Ok(())
 //! # }
@@ -121,8 +121,8 @@ impl<'a> DecodeValue<'a> for Cipher<'a> {
             let digest = OctetStringRef::decode(nr)?.into();
             let cipher = OctetStringRef::decode(nr)?.into();
             Ok(Cipher {
-                x: Uint::from_be_bytes(zero_byte_slice(x)?),
-                y: Uint::from_be_bytes(zero_byte_slice(y)?),
+                x: Uint::from_be_bytes(zero_pad_byte_slice(x)?),
+                y: Uint::from_be_bytes(zero_pad_byte_slice(y)?),
                 digest,
                 cipher,
             })
@@ -164,7 +164,7 @@ fn xor(c2: &mut [u8], ha: &[u8], offset: usize, xor_len: usize) {
 }
 
 /// Converts a byte slice to a fixed-size array, padding with leading zeroes if necessary.
-pub(crate) fn zero_byte_slice<const N: usize>(
+pub(crate) fn zero_pad_byte_slice<const N: usize>(
     bytes: &[u8],
 ) -> elliptic_curve::pkcs8::der::Result<[u8; N]> {
     let num_zeroes = N
diff --git a/sm2/src/pke/encrypting.rs b/sm2/src/pke/encrypting.rs
index b877717f..82d274e7 100644
--- a/sm2/src/pke/encrypting.rs
+++ b/sm2/src/pke/encrypting.rs
@@ -191,7 +191,7 @@ fn encrypt(
 fn next_k(bit_length: u32) -> U256 {
     loop {
         let k = U256::random_bits(&mut rand_core::OsRng, bit_length);
-        if k.is_zero().unwrap_u8() == 0 && k <= Sm2::ORDER {
+        if !<elliptic_curve::subtle::Choice as Into<bool>>::into(k.is_zero()) && k < Sm2::ORDER {
             return k;
         }
     }