# For what does “Rcon” stand for in Rijndael/AES?

How do we expand the abbreviation “Rcon” used in the Rijndael key schedule?

I know what it is, I know how it works; I just do not know for what it is a shortcut for. I mean: if "Sbox" is "Substitution box", then "Rcon" stands for… ?

• All my life, I have been sure that Rcon means round constant. (But I haven't found a credible reference to back that claim so far.) – yyyyyyy Apr 2 '16 at 19:07
• @yyyyyyy For a credible reference, check page 11 of csrc.nist.gov/publications/fips/fips197/fips-197.pdf – e-sushi Apr 3 '16 at 8:14