This is the output from W.15.14.0013 on a 2910al
sw-test-01(config)# encrypt-credentials
pre-shared-key Set key for encrypting credentials in configuration.
<cr>
sw-test-01(config)# encrypt-credentials pre-shared-key
hex Set key as 64 hexadecimal character string (32 bytes).
plaintext Set key using a plaintext string (passphrase).
sw-test-01(config)# encrypt-credentials
**** CAUTION ****
This will encrypt all passwords and authentication keys.
The encrypted credentials will not be understood by older software versions.
The resulting config file cannot be used by older software versions.
It also may break some of your existing user scripts.
Before proceeding, please save a copy of your current config file, and
associate the current config file with the older software version saved in
flash memory. See "Best Practices for Software Updates" in the Release Notes.
A config file with 'encrypt-credentials' may prevent previous software
versions from booting. It may be necessary to reset the switch to factory
defaults. To prevent this, remove the encrypt-credentials command or use
an older config file.
Save config and continue (y/n)?