Code Words

Authors of recommendation letters often add a secret layer of meaning hidden beneath the surface of a letter that is ostensibly positive.

• All of his colleagues are astounded by his scrupulous attention to detail and the zeal with which he shares this information.

• Let us just say that his strength is his weakness.

• Bold words and sweeping statements are his friend.

• We continue to be amazed by his ability to whip off articles, journal papers, and conference talks with such a minimal time in the lab.

• This candidate is a master of the art of not saying what he means. He slips quickly between two-faced disinformation and carefully worded calumny.

17.1 Finding Hidden Messages

Many of the techniques in this book are far from perfect. A wise attacker can identify files with hidden information by looking carefully for some slight artifacts created by the process of hiding information. In some cases, the tests are simple enough to be automated with a high degree of reliability. This field is often called steganalysis, a term that mimics the word cryptanalysis, the study of breaking codes.

The field of steganalysis is usually more concerned with simply identifying the existence of a message instead of actually extracting it. This is only natural because the field of steganography aims to conceal the existence of a message, not scramble it. Many of the basic tests in steganalysis will just identify the possible existence of a message. Recovering the hidden data is...