Rijndael cipher is an advanced encryption standard (AES) algorithm used for encrypting and decrypting data. It was developed by Belgian cryptographers Vincent Rijmen and Joan Daemen in 2001, with the intention of replacing the aging Data Encryption Standard (DES).

The algorithm has been adopted by the US government as their official encryption standard, due to its strong security features.

The Rijndael cipher operates on a block size of 128 bits and supports key sizes up to 256 bits long. This makes it one of the most secure algorithms available today, since it can handle larger amounts of data than other algorithms such as DES or 3DES which have smaller blocksizes.

Additionally, it uses a substitution-permutation network structure instead of relying solely on linear operations like DES does; this provides greater resistance against differential cryptanalysis attacks that target certain patterns in plaintexts when encrypted using linear operations alone.

Overall, Rijndael is considered one of the best symmetric key ciphers currently available thanks to its high level security features combined with efficient performance characteristics across different platforms including hardware implementations like smart cards or FPGAs.

Its widespread adoption among governments worldwide further attests to its popularity amongst cryptography professionals who value both reliability and efficiency when selecting an appropriate cryptographic solution for their organization’s needs.