Ángel
  • Member for 7 years, 4 months
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5 answers
9 votes
12k views
Two different keys decrypting same content
Accepted answer
14 votes

Most public key encryption schemes, such as PGP, support this. When you are encrypting a message to Bob, in fact you are encrypting the message with a random key using a symmetric cipher, then ...

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4 answers
6 votes
1k views
Bits of entropy needed to choose a random element from a list?
5 votes

You would need $ log_2 N$ bits of entropy. So from a formal point of view, from a list of 10 elements, you would need $3.321928$ bits of entropy. However, if you actually want to fetch a random ...

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1 answers
1 votes
53 views
Attacking a variation of the Vigenere with very long key length
3 votes

The important part about the length is how many letters appear on those 17 characters: YVBCXGJRYHHRCJIUL WEDNESDAYTHURSDAY WEDNESDAYSATURDAY We have the plaintext of 12 of the 17 characters. This ...

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4 answers
12 votes
10k views
How do I detect a failed AES-256 decryption programmatically?
3 votes

Ilmari Karonen already mentioned using an authenticated encryption mode, which would solve the concerns, but should you not go that way, please note the flaw in your premise: If one provides the ...

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4 answers
6 votes
1k views
Using public key cryptography with multiple recipients
2 votes

I have a message that I want to send to multiple recipients. Fine Can I encrypt the message separately with each of the recipient's public keys, Actually, when we talk about encrypting a message ...

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13 answers
12 votes
2k views
Cryptography elements needed for a story
2 votes

I don't really like your setup. Party A has available state-of the-art tech, yet party B wins because they are the good guys while they are both doing basically the same is a bit unrealistic. It could ...

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2 answers
2 votes
141 views
Prove that you have the data when hash is public
1 votes

(1) Yes, it would be a concern. Once upon a time, Dropbox did this. When synchronizing the files, it checked the hashes before uploading. Thus, if the file was already in their servers, they just ...

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2 answers
1 votes
130 views
Break HMAC-SHA256 of PAN with known hash?
Accepted answer
1 votes

Only for a trivial key. You have HMAC(<key>, <secret₁>) = <hash>. The attacker knows <hash> and certain <secret>. Having a small search space, different <secret> ...

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7 answers
51 votes
10k views
One Encryption, Many Decryption Keys
1 votes

There's something odd with your description: If you give access to Alice and Bob today, but you must be able to give Charlie access tomorrow if he signs up, you need to have access to the data, either ...

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3 answers
0 votes
61 views
Is there an accepted way to cryptographically enforce tracked changes on a document?
0 votes

The goal is to allow one user to lock tracked changes with a password, which would allow other users to only edit the document with tracked changes. Any edit to the document that is not tracked would ...

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1 answers
1 votes
66 views
Encrypting data with two separate keys
Accepted answer
0 votes

I would say that all of them are valid options, with the security differences they might have negligible. So I focused on other properties of the approaches: Option 1: XOR I think the most interesting ...

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2 answers
0 votes
119 views
How do I calculate Base64 conversion rate?
0 votes

base64 is defined on rfc4648 As poncho mentions, it has an overhead of 33%, and thus 96 / 4 × 3 = 72 bytes needed

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