First log onto your SharePoint server and go to Start | All Programs | Microsoft SharePoint 2010 Products | SharePoint 2010 Management Shell also right click the link and run as administrator.
Next step at the PowerShell prompt input
$passphrase = ConvertTo-SecureString -asPlainText –Force
You will be prompted to input a new passphrase in plain text. Next step is to input
Set-SPPassPhrase -PassPhrase $passphrase –Confirm
After inputting the command above you will be asked to reenter the new passphrase this time it will be hashed then it is just a simple case of entering Y(Yes) N(No) to complete the change
