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Why are bits important?

CS110: Computer Science and the Internet. Why are bits important?. What do these bits represent?. 01000011 01010011 00110001 00110001 00110000 00100000 01101001 01110011 00100000 01100110 01110101 01101110. Decimal numbers? 83 49 49 32 105 115

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Why are bits important?

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  1. CS110: Computer Science and the Internet Why are bits important?

  2. What do these bits represent? 01000011 01010011 00110001 00110001 00110000 00100000 01101001 01110011 00100000 01100110 01110101 01101110 Decimal numbers? 83 49 49 32 105 115 32 102 117 110 Image clip? String of text? CS110 is fun Bits are universal and ubiquitous and Bits have no intrinsic meaning

  3. Scenario #1 You’d like to donate your old laptop to a charity or school, and have sensitive information on the laptop such as your social security number, banking information or personal photos, that need to be removed. What should you do to prepare your laptop before giving it away? Bits can be forever… MAC: “Empty Trash…” vs. “Secure Empty Trash…” (similar for PC) “Sanitizing” software

  4. Scenario #2 You work for a technical firm that’s about to issue a press release for an exciting new product. The release will be posted as a PDF file on the company website. The current document contains proprietary information with key design details. You’re asked to “redact” these details before releasing the document. How should you carry out this redaction? What lies beneath… What you see is not what you get! captain.pdf “Redacting with confidence: How to safely publish sanitized reports converted from Word to PDF”

  5. Secret messages… What’s different about these two images? Red components for first 8 image pixels (before) 01000011 01010011 00110001 00110001 . . . 00110000 00100000 01101001 01110011 Red components for first 8 image pixels (after) 01000010 01010011 00110000 00110000 . . . 00110000 00100000 01101001 01110011 01000011 is 67 in decimal, which represents “C” in the ASCII code Decoding the first 208 pixels: “CS110 quiz key 1C 2B 3A 4D"

  6. Manipulating bits Bits can easily be changed! so how can we trust the integrity of electronic information? Stenography • Bits can be manipulated by general algorithms, for good reasons: • Error reduction • Compression • Encryption • Digital Fingerprinting MD5 “fingerprint”: mad-men-denouement.pdf 1ae19daa3fd404c5635819d4b0428a23 JanuaryJones.pdf: 8f0af5376c500c41f902f330925f717eJonHamm.pdf: 973a14a33c9f092906566b2a327f57a9

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