Function decrypt 

pub fn decrypt(
    private: &Sm2PrivateKey,
    ciphertext_der: &[u8],
) -> Result<Vec<u8>, Error>

Decrypt a GM/T 0009 DER-encoded ciphertext under recipient private key private.

Returns Ok(plaintext) on success, crate::Error::Failed on any failure.

Errors

See module-doc — every failure mode collapses to one variant.