Bob's encrypted message

Bob is an employee of a company working in special department that develops sensitive projects. Many of information that regards the daily work are exchanged between the team members using the company’s email system. For privacy reason they always are using S/MIME encryption. In order to maintain a higher security level, the company’s security stuff asked that each of the employee have to use a dedicated hardware device as cryptographic token to store his private keys in good security conditions. The cryptographic tokens are very suitable to protect the keys, and always require PIN-based authentication before allow the access to the keys.

However, one problem is that sometimes some of the employees do not take fully account of these requirements. For example, to gain flexibility they like to have several copies for their private keys. In this way, sometimes they export the private keys outside the token and store them in password-based encrypted files on the hard drive. Worse than that, to simplify the things they often choose to use the same password as on the token to protect the key. This scenario could really provide flexibility and ease of use but it could be also a big security hole.

In this task, you can prove the threat. Your mission is to recover sensitive information sent by one to Bob using encrypted email messages. You can assume that you already intercepted one of these mails and you have accessed the hard drive of Bob’s working station extracting from there the file Bob.prv.  The flag is the sensitive information from Bob’s email.