RSA SecurPC is a software utility that encrypts disks and files on both desktop and laptop personal computers. SecurPC extends the WindowsTM File Manager or Explorer to include options for encrypting and decrypting individually selected files or files within selected folders. Each file is encrypted using RC4 (see Question 3.6.3) with a randomly generated 128-bit key (40 bits for some non-U.S. users.) The random key is encrypted under the user's secret key, which is encrypted under a key derived from the user's passphrase. This allows the user's passphrase to be changed without decrypting and reencrypting all encrypted files.
SecurPC provides for optional emergency access to encrypted files, based on a k-of-n threshold scheme. The user's secret key may be stored, encrypted with the RSA algorithm, under an emergency access public key. The corresponding private key is given, in shares, to any number of trustees. A designated number of these trustees must present their shares in order to decrypt the encrypted files.
SecurPC has been superseded by RSA Security's Keon Desktop, but some information about the product may still be found at http://www.solwaycomms.co.uk/.