A USB Crypto token securely stores your DSC with Strong passwords. Further it provides mobility to your DSC when you have to perform signing on multiple computers. Your digital signature is vulnerable to key compromise if many users access the same machine on which you sign the documents with you DSC. However the same can be avoided with the help of a token. CCA (Controller of Certifying Authorities)  vide its office order dated 25th Oct 2013 has mandated issuance of class 2 and class 3 digital signatures on a FIPS level 2 cerified token