@CryptographyTip

Daily posts about cryptography

johndcook.com/
Joined January 2024
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MD5 hash collision example johndcook.com/blog/2024/03/2…

MD5 hash collision example

Demonstrating an MD5 hash, how to compute hash functions in Python, and how to diff strings.

johndcook.com
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The PQC Migration Handbook: Guidelines for migrating to post-quantum cryptography marc-stevens.nl/research/pap… [pdf]
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Binary to text to binary johndcook.com/blog/2024/01/1…

Binary to text to binary with GPG enarmor and dearmor

Gnu ASCII armor can be used to convert any file from binary to a text file and back. Written for encryption but useful for any file.

johndcook.com
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Online Playfair cipher planetcalc.com/7751/
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Order-Revealing Encryption crypto.stanford.edu/ore/
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Ring-LWE Cryptography for the Number Theorist arxiv.org/abs/1508.01375v2

Ring-LWE Cryptography for the Number Theorist

In this paper, we survey the status of attacks on the ring and polynomial learning with errors problems (RLWE and PLWE). Recent work on the security of these problems...

arxiv.org
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Weak encryption and surveillance johndcook.com/blog/2023/12/3…

Weak encryption and surveillance

Evading commercial surveillance is much easier than evading intelligence agencies. Ridiculously insecure methods may be adequate for the former.

johndcook.com
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Montgomery curves and their arithmetic eprint.iacr.org/2017/212.pdf [pdf]
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STRONG encryption may not be sufficient for legal protection. Some laws require STANDARD encryption. johndcook.com/blog/2024/03/2…

Breach Safe Harbor

Breach Safe Harbor refers to the breach of encrypted health information

johndcook.com
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Perfect nonlinear functions and cryptography sciencedirect.com/science/ar…
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Graph of what papers report for costs of attacks against ChaCha6 and ChaCha7. ChaCha8 is untouched so far, but, as always, my recommendation is to use 20 rounds except when speed constraints force usage of 12 or 8. Graph comes from my latest McEliece talk: cr.yp.to/talks.html#2025.03.…
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Cypherpunks: Freedom and the Future of the Internet ia903007.us.archive.org/22/i… [pdf]
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What is the point of a public key fingerprint? johndcook.com/blog/2023/12/1…

What is the point of a public key fingerprint? PGP GPG

What is the point of a public key fingerprint? What does it do that the public key itself doesn't do. This post explains.

johndcook.com
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ELSA: Efficient Long-Term Secure Storage of Large Datasets arxiv.org/abs/1810.11888
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A Graduate Course in Applied Cryptography crypto.stanford.edu/~dabo/cr… [pdf]
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ASCII armor: Send encrypted data in plain text johndcook.com/blog/2023/12/1…

GnuPG ASCII armor: send encrypted data in plain text | GPG

How GPG's ASCII armor works, converting binary data into a human-friendly ASCII form, as human-friendly as possible given the task.

johndcook.com
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Polish Mathematicians Finding Patterns in Enigma Messages jstor.org/stable/27643040

Polish Mathematicians Finding Patterns in Enigma Messages | JSTOR

Chris Christensen, Polish Mathematicians Finding Patterns in Enigma Messages, Mathematics Magazine, Vol. 80, No. 4, Oct., 2007

jstor.org
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Imperfect Forward Secrecy: How Diffie-Hellman Fails in Practice microsoft.com/en-us/research… [pdf]
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Victorian public key cryptography johndcook.com/blog/2023/09/2…

Victorian public key cryptography

Would public key cryptography have been possible before electronic computers?

johndcook.com
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