r/crypto

42K archived posts · Dec 2008 – Sep 2026

Cryptography news and discussions

r/crypto

Cryptography is the art of creating mathematical assurances for who can do what with data, including but not limited to encryption of messages such that only the key-holder can read it. Cryptography lives at an intersection of math and computer science. This is a technical subreddit covering the theory and practice of modern and *strong* cryptography.

Created Dec 18, 2008 · restricted

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42KArchived posts

#Cryptography ... is the art of creating mathematical / information theoretic assurances for who can do what with data, including but not limited to the classical example of encrypting messages so that only the key-holder can read it. Cryptography lives at an intersection of math and computer science.

This subreddit is intended for links and discussions surrounding the theory and practice of modern and strong cryptography.

Please note that this subreddit focused on the tech, not politics! The focus is on the algorithms and the security of the implementations.

####Want to join? Because this subreddit currently is in restricted mode, you will NOT be able to post or comment before your account has been approved. Send us a reason for why you want to join via mod mail, click here and tell us why you want to discuss cryptography;

###Click HERE to send a request to join

#####NOTE: This is NOT a cryptocurrency subreddit, [see r/cryptocurrency](/r/cryptocurrency)

###RULES (along with normal reddiquette)

Don't forget to read our RULES PAGE! The rules listed there are also used as this sub's report reasons. The quick version;

Assume good faith and be kind. This is a friendly subreddit.
Using any AI / LLM without disclosing it is prohibited. You MUST inform us if you used one, AND share the prompt. They are frequently wrong and we must be able to distinguish the true source
Codes, simple ciphers, ARGs, and other such "weak crypto" don't belong here. (Rule of thumb: If a desktop computer can break a code in less than an hour, it's not strong crypto.) You're probably looking for r/codes.
Do not ask people to break your cryptosystem without first sharing the algorithm. Sharing just the output is like...
"Crack this cipher" challenges also belong in r/codes unless they're based on interesting crypto implementation bugs, e.g. weak RSA keys.
Familiarize yourself with the following before posting a question about a novel cryptosystem, or else the risk is nobody will take their time to answer:
- Kerckhoffs's principle
- Schneier's Law
Don't use this sub to cheat on competitions or challenges! You're expected to solve such problems yourself. You may ask for help to understand it, but you should disclose the source.
Systems that use crypto are not necessarily relevant here, e.g. Bitcoin. Maybe try r/cryptocurrency? Political news also very rarely belong here. See the list of related subs below for alternatives. Remember that this sub is focused on the algorithms, and isn't political.