# Tagged Questions

A commutative encryption system allows a message encrypted with two different keys to be decrypted using the keys in either order.

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### Commutative Hash Function for Password Challenge?

I had an idea. Could anyone tell me if this is a thing, if they see any problems with it, and if they know of a commutative hash function that would make it work? Suppose you had a pair of ...
332 views

### Decrypting an encrypted text out of order

Does there exist a cipher that can be encrypted twice with two different keys and then decrypted twice using either key first? For example: ...
750 views

### Public key crypto without modular arithmetic?

This comment from Reddit math, in response to a statement about how people can communicate secrets to each other with a third party listening, has a very small, simple example of public key ...
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### Are there transitive ciphers (either symmetric and asymmetric)

Say Alice has information that's already encrypted with Bob's key. She wants Bob to decrypt it without knowing what he just decrypted. So she encrypts it with her key and sends it to him, he decrypts ...
179 views

### Is there a way to prove equality of plaintext that was encrypted using different public keys?

Imagine if Alice encrypts message to Bob (using public key $P_{bob}$) and then Bob encrypts the same message to Carol (using $P_{carol}$). Is there a way for Bob to prove that: $P_{carol}$ was ...
1k views

### Are there any secure commutative ciphers?

This answer lists two commutative cipher algorithms - Pohlig-Hellman and SRA. However, they don't appear to be too secure. My question is, here there any commutative ciphers out there that are secure ...