These functions are used to encrypt and decrypt data.
krb5_encrypt puts the encrypted version of data (of size len) in result. If the encryption type supports using derived keys, usage should be the appropriate key-usage. krb5_encrypt_EncryptedData does the same as krb5_encrypt, but it puts the encrypted data in a EncryptedData structure instead. If kvno is not zero, it will be put in the kvno field in the EncryptedData.
krb5_decrypt, and krb5_decrypt_EncryptedData works similarly.