DES算法将明文分成64位大小的众多数据块，即分组长度为64位，同时用56位密钥对64位明文信息加密，最终形成64位的密文。如果明文长度不足64位，则将其扩展为64位（如补零等方法）。-DES algorithm is divided into 64-bit plaintext data block size, number of that packet length is 64, while using 56-bit key for 64-bit plaintext message encry

SPI padding options. Warning: must be a base of 2 (& operation used) and can not be zero.

SPI padding options. Warning: must be a base of 2 (& operation used) and can not be zero !.

long and has zero padding if needed.