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Phil Smith III

Mainframe Architect and System z Product Manager at Voltage Security

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Cryptography for Mere Mortals #10

I promised that we were done with hashes, but there’s one more set of interesting and powerful uses for them that’s worth discussing: Message Digests (MDs), Message Authentication Codes (MACs*), and Hashed Message Authentication Codes (HMACs). A Message Digest is just a hash of a message. MDs are useful to verify that the message was not accidentally damaged in transit. These were useful in the days of dialup and other technologies; with modern TCP/IP, not so much, although some websites will list an MD along with a download so that you can verify that you downloaded what you meant to... Continue reading

Posted Feb 21, 2013 at Superconductor

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Cryptography for Mere Mortals #9

An occasional feature, Cryptography for Mere Mortals attempts to provide clear, accessible answers to questions about cryptography for those who are not cryptographers or mathematicians. A final (maybe!) word on hashes: Q: I see that NIST has selected a new hash algorithm, to be called “SHA-3”. Does this obsolete SHA-2? A: Not really. About five years ago, there were suggestions in the crypto community that SHA-2 might be “broken” soon: that is, that there might be ways (at least in some cases, given enough hashed data) to figure out the original values that might have been hashed. As a result,... Continue reading

Posted Nov 21, 2012 at Superconductor

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Cryptography for Mere Mortals #8

An occasional feature, Cryptography for Mere Mortals attempts to provide clear, accessible answers to questions about cryptography for those who are not cryptographers or mathematicians. Q: Follow-on to Cryptography for Mere Mortals #7: How can cryptographic hashes be used to protect passwords? A: By cryptographically hashing the passwords when they’re stored, then hashing the user’s input when she tries to log on, and comparing that against the hash. This is a typical use of cryptographic hashes: to create a reference to something as a reasonably short value. You can then expose this value without exposing the original data. Thus many... Continue reading

Posted Oct 2, 2012 at Superconductor

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Cryptography for Mere Mortals #7

An occasional feature, Cryptography for Mere Mortals attempts to provide clear, accessible answers to questions about cryptography for those who are not cryptographers or mathematicians. Q: The previous installment promised to talk about “hashes”. Corned beef? A: No, a cryptographic hash is something different—not quite as tasty—although it does involve chopping the input into small pieces. This installment is the first of several that present a simplified discussion of hashes and related technologies. Wikipedia says, in part: A cryptographic hash function is a hash function, that is, an algorithm that takes an arbitrary block of data and returns a fixed-size... Continue reading

Posted Aug 14, 2012 at Superconductor

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Cryptography for Mere Mortals #6

Cryptography for Mere Mortals #6 An occasional feature, Cryptography for Mere Mortals attempts to provide clear, accessible answers to questions about cryptography for those who are not cryptographers or mathematicians. Q: Is it really as easy to hack into someone’s computer or a website, or to decrypt an encrypted file, as they show it in the movies? A: No, no, and no! This is worth repeating because folks don’t understand it, and get all kinds of wild ideas about passwords as a result. OK, having said that…actually the real answer is “sometimes, maybe”. But certainly not the way they do... Continue reading

Posted Jul 11, 2012 at Superconductor

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Cryptography for Mere Mortals #5

An occasional feature, Cryptography for Mere Mortals attempts to provide clear, accessible answers to questions about cryptography for those who are not cryptographers or mathematicians. Q: How do we know whether a given encryption solution will produce unique results—that is, that for each unique input, a unique output will result? If, say, two SSNs both encrypt to the same value, we’ll have a huge mess on our hands! A: This is one of the reasons that a security proof is important. It’s easy to say “Sure, it’ll be unique”, but without a careful, peer-reviewed security proof, such a statement has... Continue reading

Posted May 31, 2012 at Superconductor

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Cryptography for Mere Mortals #4

An occasional feature, Cryptography for Mere Mortals attempts to provide clear, accessible answers to questions about cryptography for those who are not cryptographers or mathematicians. Q: What do people mean by “Data Masking”? A: This is a confusing term, because it can mean at least two different things, both related to data protection/privacy: 1. Encrypted or tokenized data that is converted back to plaintext, but with some of the characters “masked” by characters such as “x” or “*”;for example, a Social Security number of “999-88-1234” might be returned as “XXX-XX-1234” 2. Production data that is obscured or obfuscated for testing... Continue reading

Posted Apr 20, 2012 at Superconductor

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Cryptography for Mere Mortals #2

An occasional feature, Cryptography for Mere Mortals attempts to provide clear, accessible answers to questions about cryptography for those who are not cryptographers or mathematicians. Q: How does one “attack” encryption? A: Either by: 1) analyzing a large number of ciphertexts and matching plaintexts and looking for patterns, or 2) brute force—trying all the possible keys. Note that the analysis approach involves some “cheating”: it’s not particularly likely that a random attacker will have this much information to work with. But if the crypto resists analysis even under those circumstances, it’s at least as secure in a more realistic scenario.... Continue reading

Posted Feb 21, 2012 at Superconductor

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Cryptography for Mere Mortals #1

An occasional feature, Cryptography for Mere Mortals attempts to provide clear, accessible answers to questions about cryptography for those who are not cryptographers or mathematicians. Q: Isn’t Format-Preserving Encryption easy to break because the output is all plaintext, so there are fewer possible ciphertexts? For example, if you encrypt a four-digit number, there are only 10,000 possibilities. A: No. The strength of the encryption is based on the key size, not the number of possible outputs. So for 128-bit AES, there are 2128 possible keys, no matter how short the input is. Certainly it is true that, since there are... Continue reading

Posted Feb 17, 2012 at Superconductor

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