The User Guide for the SNMP product incorporated into AM says it is the "first Java SNMP product to support both DES and strong 128-bit AES encryption algorithms."
The same User Guide states in response to the Question: Q. How's the SNMPv3 support?
"SNMP library fully supports SNMPv3, including the complete
VACM and USM security model (HMAC-MD5, HMAC-SHA1, HMAC-SHA2,
CBC-DES, CFB128-AES-128, CFB128-AES-192, CFB128-AES-256)."
Note, RSA Authentication Manager is currently at AM 8.4 P9. The SNMP User Guide had a copywrite of 2016. So this information might apply to your AM 8.1, or it might not, but considering AM 8.1 is pretty old, you should consider updating.
Here's a 10 minute how to video