由于CBC－MAC模式不可并行处理，提出了一种基于双重分组的并行认证模式(PKCB)。PKCB模式同并行认证模式PMAC相比，安全性和速率都有显著提高，PKCB认证模式与CTR（计数器）加密模式结合可构成分组密码算法的一种全工作模式。在此基础上提出了一种基于密钥计数的并行认证模式（KCTR－MAC）。KCTR－MAC模式安全性比PMAC模式高得多，而速率未降低，KCTR－MAC认证模式和CTR加密模式结合也可构成分组密码算法的一种全工作模式（2CTR），2CTR模式的综合性能不亚于标准模式CCM（CTR with CBC－MAC），是一种安全快速的实用模式。

The CBC - MAC mode is not a parallel one. A parallel authentication mode (PKCB) based on double blocks was put forward in this paper. The PKCB mode had a marked improvement on security & speed over parallel authentication mode, PMAC. And it may be combined with the CTR (counter) encryption mode to form a full block cipher mode. On this ground, another parallel authentication mode (KCTR - MAC) based on key counter was advanced. As compared with the PMAC mode, the KCTR - MAC mode had a marked improvement on security, while its speed did not become lower. The KCTR - MAC authentication mode may be combined with the CTR (counter) encryption mode to form a full block cipher mode (2CTR)，too. The 2CTR mode had a performance advantage over the standard mode, CCM (CTR with CBC - MAC). And it was a fast, practicable mode with security.