We implemented the AES (Advanced Encryption Standard) block based on its standard. Any analysis of the strengths and weaknesses of AES is performed by the standard's committee.
Studies for the strength of AES encryption key have been documented by the standard's committee in the link below, specifically section 6.2 of the document in the below link says that there's no restriction on the key:
http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf
但是，上面的文档于2001年发布。从那时起，存在理论攻击方案。其他资源：
http://www.quadibloc.com/crypto/co040401.htm
http://en.wikipedia.org/wiki/advanced_Encryptim_candard
第一页有有关“攻击Rijndael”的部分。这似乎暗示着所有常数的键都不好。