In this paper,we examine the security of reduced AES-192 and AES-256 against related-key rectangle attacks by exploiting the weakness in the AES key schedule. We find the following two new attacks:9-round reduced AES-192 with 4 related keys,and 10-round reduced AES-256 with 4 related keys. Our results show that related-key rectangle attack with 4 related keys on 9-round reduced AES-192 requires a data complexity of about 2101 chosen plaintexts and a time complexity of about 2174.8 encryptions,and moreover,related-key rectangle attack with 4 related keys on 10-round reduced AES-256 requires a data complexity of about 297.5 chosen plaintexts and a time complexity of about 2254 encryptions. These attacks are the first known attacks on 9-round reduced AES-192 and 10-round reduced AES-256 with only 4 related keys. Furthermore,we give an improvement of the 10-round reduced AES-192 attack presented at FSE2007,which reduces both the data complexity and the time complexity.
