AD RMS can operate under two modes which differ on the basis of the cryptographic key length and the strength of signature ...

AD RMS can operate under two modes which differ on the basis of the cryptographic key length and the strength of signature hashes. Cryptographic mode 2 is recommended for new cluster deployments where you have ensured that all AD RMS client computers have been updated to support it. As cryptographic mode 2 cannot be undone, if you are unsure of full support within this cluster or any other clusters that it will share a trusted user domain (TUD) relationship with, select cryptographic mode 1 instead.