29日美国联邦调查局（FBI）在网站上发布了新的密码破解挑战赛。密码由FBI专家创造，去年FBI也推出过类似的邀请黑客参与的挑战比赛，它声称收到了数万个答案。FBI还在网站上向读者介绍了最基本的密码知识，如凯撒密码（Caesar cipher）： 明文：A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
暗文：B C D E F G H I J K L M N O P Q R S T U V W X Y Z A 在上例中，明文字母K被密码译成J，那么短语“Lucky Dog”用密码书写就是“M V D L Z E P H”。当然为了让密码更安全，可以使用关键词打乱排列顺序，比如用关键词SECRETLY（去除第二个E），那么现在的 明文：S E C R T L Y A B D F G H I J K M N O P Q U V W X Z
暗文：A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

FBI issues code cracking challenge

By Layer 8 on Mon, 12/29/2008 - 12:35pm.

The FBI today challenged anyone in the online community to break a cipher code on its site.  The code was created by FBI cryptanalysts. The bureau invited hackers to a similar code-cracking challenge last year  and got tens of thousands of responses it said.

A number of sites host such cipher challenges, including this one at the University of South Hampton.

The FBI offers a few primers on the subject including:

A relatively basic form of substitution cipher is the Caesar Cipher, named for its Roman origins. The Caesar Cipher involves writing two alphabets, one above the other. The lower alphabet is shifted by one or more characters to the right or left and is used as the cipher text to represent the plain text letter in the alphabet above it.

Plain Text

A B C  D E F G H I J K L M N O P Q R S T U V W X Y Z

Cipher Text

B C D E F G H I J K L M N O P Q R S T U V W X Y Z A

In this example, the plain text K is enciphered with the cipher text L. The phrase 'Lucky Dog' would be enciphered as follows:

Plain Text: L U C K Y D O G

Cipher Text: M V D L Z E P H

Ciphers can be made more secure by using a keyword to scramble one of the alphabets. Keywords can be placed in the plain text, the cipher text, or both, and any word can be used as a key if repeated letters are dropped. Here the word SECRETLY (minus the second E) is used as the plain text keyword.

Plain Text

S E C R T L Y A B D F G H I J K M N O P Q U V W X Z

Cipher Text

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

The FBI of course doesn't always invite folks to break code on its site. In fact last spring a consultant managed to access the bureau's National Crime Information Center database.

Headline Archives

CODE BREAKERS A 400-Year History of Cryptanalysis 04/12/06 A coded message of the "Zodiac" serial killer that was broken by a California couple in a few hours. Ted Kaczynski—the infamous "Unabomber"—used them. So did Russian spies like Rudolf Abel. Not to mention John Wilkes Booth and Mary, Queen of Scots. We're talking about secret codes and ciphers...used in the commission of crime, espionage, and terrorism. Find out how law enforcement broke these and other codes with "cryptanalysis" in Code Breaking in Law Enforcement: A 400-Year History in the new issue of Forensic Science Communications. The article was written by one of our own cryptanalysts, Dorn Vernessa Samuel, who works in the Cryptanalysis and Racketeering Records Unit in the FBI Laboratory. Here are a few of the cases featured: Murder He Wrote. While in jail awaiting trial for the 2004 murder of an 11-year-old Florida girl, Joseph Peter Smith sent his brother a coded message. Authorities asked us to analyze it, and our cryptanalysts quickly broke the code. It wasn't easy: Smith had replaced letters of the alphabet with a series of number/symbol combinations written from right to left and from the bottom of the page going up. In the letter, Smith made incriminating references to moving the body and hiding evidence, and he was ultimately convicted of the crime. All in the Family. Code-breaking pioneers Elizebeth Friedman and her husband William were considered the "greatest marriage in the history of cryptology." Elizebeth, a Treasury Department cryptanalyst, unraveled bootleggers' ciphers during Prohibition, solved a Chinese code that broke up an opium smuggling ring (even though she didn't know the language), and helped settle a maritime dispute between the U.S. and Canada (see the article for the interesting details!). A U.S. Army cryptologist who coined the term "cryptanalysis", William decrypted Japanese diplomatic messages during World War II and secret telegrams in the 1924 Teapot Dome Scandal that led to the resignation of top U.S. officials. North versus South. Both Union and Confederate forces used ciphers during the Civil War. Confederates were less successful in figuring out Union codes, though, and started publishing them in Southern newspapers, imploring readers to break them. John Wilkes Booth and his conspirators supposedly used ciphers as well to coordinate plans to assassinate President Lincoln. If you want to learn more on the subject of code breaking, including details on basic cipher systems and how to break them, see the article Analysis of Criminal Codes and Ciphers in a previous issue of Forensic Science Communications. And direct your grade-school children to our Kids' page, which has a secret message to decode for fun.

Headline Archives

  CAN YOU CRACK A CODE?
Try Your Hand at Cryptanalysis   11/21/07  

The “cryptanalysts” who work in our FBI Laboratory are experts in breaking codes and ciphers of all kinds, but this time we asked them to create one for us just for fun. 

 

Your mission—if you choose to accept it—is to crack the code below and reveal the hidden message. 

 

Hint:  if you want a primer on basic cipher systems and how to break them, see the article Analysis of Criminal Codes and Ciphers. 

 

And if you’re a youngster, we recommend that you start with the code on our Kids' page.

Good luck!

To learn more about code-breaking in the FBI: 

• A 400-Year History of Cryptanalysis
• The Zodiac Killer Case 
• The FBI Lab Annual Report