Implementing-cryptography-using-python

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Chapter 6 ■ Using Cryptography with Images 197blue = fits.PrimaryHDU(data=b_data)blue.header["AUTHOR"] = authorblue.header["LATOBS"] = location_latblue.header["LONGOBS"] = location_longblue.header["SATNAME"] = satelliteblue.writeto('chapter6/fits/blue.fits', overwrite=True)The output of the previous code takes our secret image from the beginningof the chapter and creates three unique FITS files using red, green, and bluechannels. You will see in Figure 6.15 that the header for green.fits contains oursecret information. As you might expect, we could easily encrypt the image too.Figure 6.15: FITS FilesSummaryIn this chapter, you were introduced to a couple of libraries that perform cryptographicand steganography tasks on images. It is important for you to understandhow various AES block modes work and how they apply to image files.We concluded the chapter by using the CryptoSteganography library to hidevarious types of files. Hiding messages inside an image could affect the propertiesof the image. This was obvious when we hid a 30-second MP3 file insidean image. The decryption process for each of these examples is dependent onthe use of a secret key; if the recipient of the file does not have the secret key,your message will remain a secret even if the recipient can see that the visualproperties of the file have changed. Finally, we explored the FITS file format.While the FITS format may not provide much value on the surface, the amountof data that can be stored and encrypted is incredible.
CHAPTER7Message IntegrityYou should be comfortable at this stage with symmetric key cryptography. Inthis chapter, you learn to generate message authentication codes to let messagerecipients validate that the message they are receiving has not been tamperedwith while it was in transit. In the context of message integrity, a hash functionis used to produce a fixed-length message digest from a variable-size message.The most common message digests range in length from 160 to 512 bits. Anyalteration to the input message produces a dramatically different message digest.The message digests help detect unauthorized alterations and message forgeries.The principles you learn and develop here continue in the next chapteras you explore public-key cryptography; throughout this chapter, you gaincryptographic knowledge as you:■■Learn about Message Authentication Codes (MACs)■■Ensure that your signature is not compromised and does not get forged■■Explore how to make forgeries when someone else failed to protect theirsignatures■■Explore sending encrypted data over nonsecure channelsImplementing Cryptography Using Python®, First Edition. Shannon W. Bray.© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.199
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ImplementingCryptography UsingPytho
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To Stephanie, Eden, Hayden, and Ken
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viAbout the Authorbook, Shannon is
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Contents at a GlanceIntroductionxvi
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xiiContentsUsing Conditionals 16Usi
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xivContentsPseudorandomness115Break
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xviContentsInstalling and Testing W
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xviiiIntroductionprivacy advocates.
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CHAPTER1Introduction to Cryptograph
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Chapter 1 ■ Introduction to Crypt
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CHAPTER2Cryptographic Protocolsand
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Chapter 2 ■ Cryptographic Protoco
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66 Chapter 3 ■ Classical Cryptogr
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CHAPTER4Cryptographic Mathand Frequ
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Chapter 4 ■ Cryptographic Math an
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CHAPTER5Stream Ciphers and Block Ci
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Chapter 5 ■ Stream Ciphers and Bl
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Chapter 9 ■ Mastering Cryptograph
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IndexSYMBOLS\ (backslash), 10- oper
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Index ■ D-D 279CIA Triad, 35-36ci
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Index ■ I-M 281hashlib module, 28
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Index ■ Q-S 283Preneel, Bart, 145
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