A one-time pad is an encryption method that uses a key (the pad) that is as long as the message. It provides perfect secrecy but at the cost of having as much key data as payload. Not to be confused with one-time passwords.

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Why even use a one-time pad if the key distribution is fully secured?

I had a job interview yesterday where they asked what the only scenario where a one-time pad can be broken would be, my answer to which was "when the key distribution process is not secure enough". ...
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1answer
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One-Time-Pad Decryption [closed]

For homework, I have a ciphertext which is 582 chars long. The OTP used was reused over and over. The OTP is 50 chars long. How exactly can I now get the key and the cleartext?
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1answer
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Infinite one time pads, brute force multiple pads?

So based on my understanding using the same key for encrypting two completely random plain texts when using an otp cipher will still retain perfectly secret. This is based on the answers on this ...
3
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1answer
106 views

What are the problems of using OTP encryption with TRNG?

I've programmed a simple One-Time Pad "encryptor" that can merge two files into one by using bitwise XOR. The pseudo-random key files are generated by using the CryptGenRandom() function from ...
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2answers
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Is One-Time pad used anywhere?

One-time pad is a method where you XOR plaintext with the key. If the key is be random and not used more than one then the one-time pad is unbreakable. Another advantage is easy implementation. ...
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1answer
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Unconditionally Secure Authentication

I'm trying to add the authentication for my One-Time Pad implementation. I know that to provide Unconditionally Secure Authentication I need to use the One-Time MAC authentication. But I don't ...
1
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1answer
127 views

One-Time Pad authentication & Information-theoretic security

I'm trying to create a "Information Theoretically Secure" cryptosystem, inspired on the One-Time Pad. Now I'm facing the obstacle of authentication... How good is this solution (that uses the "Encrypt ...
3
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2answers
346 views

Can this modified 'Many' Time Pad be made 'stronger' by using an extrememly long key?

Starting with a one time pad say you want to encrypt some small strings like the words in this sentence but you want to reuse the same OTP key for each string so that when you encounter the same word ...
28
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7answers
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Can you say that since one time pad encryption is unbreakable, it is the best if used properly?

I'm currently reading about one time pad encryption, and I have a question. They say OTP encryption is unbreakable, and this can be proved mathematically. This is provided that the key used is truly ...
0
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1answer
134 views

How does a keyfile work?

I was looking at some code on codereview that is far out of my league of understanding and just screwing around, but it raised a question. This program (along with many other encryption programs, i ...
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1answer
546 views

Best practices for usefully storing two factor authentication backup codes?

For a lot of web services offering two factor authentication, after setting up the system, you are given a short list of backup codes (one-time pads) that are around 7-10 characters long. These are ...
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1answer
178 views

How to cryptoanalyze a one time pad that uses a plain text document as the pad?

I have read that in order for a one time pad to be truly secure, the pad itself must be random data. Given the practical difficulty of sharing a secure random pad, I was wondering what would be the ...
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3answers
432 views

Is breaking a looping one-time pad practical? If so, how?

A one-time pad is known to be theoritcally secure, nothing can break it. However, if the key is reused, the one time pad becomes theoritically breakable. But even RSA is theorically breakable yet it'...
3
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1answer
256 views

How to fix this broken crypto protocol?

I am considering a protocol where you upload a one time pad to a server, using public key encryption and then the result (using the pad) is sent back in plaintext: Alice uses Bobs RSA public key to ...
3
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5answers
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Advantages of one time pad

I always hear that one time pad'ing something is so great because you won't know if you've successfully decrypted the data. I understand the idea that you can XOR any bits just the same as any other ...
18
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9answers
4k views

Are there any systems out there that use a one-time pad?

I'm still new to information security, but I have read a bit about the one-time pad. The point that sticks out to me the most is that it is supposedly unbreakable. Has this method of encryption ever ...
0
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1answer
99 views

How strong is this encryption? [closed]

Given Dictionary containing 1000 three-letter words: dictionary=abc,def,ghi,jkl,mno,pqr... Randomly chosen words from the dictionary: 10-bits-passwords=abc,def,ghi Randomly chosen three words from ...
3
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1answer
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How to Encrypt Credit Card number for storing it in sql server database according to PCI DSS Requirement?

According to PCI-DSS 3.4 Requirement: Render PAN unreadable anywhere it is stored by using the below methods: One-way hash Truncation Index tokens and pads Strong cryptography with associated key-...
5
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2answers
430 views

How to use one time pad if the key is shorter than the plaintext?

I understand that one of the requirements (and a major drawback) of OTP is that the key has to be as long as the message is. What happens if I have a key that is shorter? The message would only get ...
1
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2answers
495 views

What is (“ASCII” redundancy) which is said to be required to retrieve the original plain text in 2 times pad?

Sorry for the long title :$ In a video speaking about attacks on the one time pad which uses psudorandom generators (PRG), It's said that Eve can retrieve the plain text of 2 messages that have been ...
0
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2answers
597 views

An attempt to overcome the key distribution problem inherent in one time pad cryptography

After reading about the 'imminent cryptocalypse' etc, I started thinking about a cryptographic protocol that would not depend on complexity of mathematical operations (e.g. factorisation, discrete ...
0
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3answers
814 views

Is using a numbers station to transmit a one-time-pad as key actually insecure?

We all know the two most important problems related to a “one-time-pad”: The one-time-pad needs to be truly random (which I think is logic, as pseudo random generators are quick but predictable). ...
6
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2answers
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Decrypt cipher texts encypted with the same one time pad key

I have two pieces of ciphertext encrypted with a stream cipher using the same key. How do I recover the plaintext of both ciphertext messages without knowing the key used?
6
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2answers
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Why is using a pseudo-random key considered more practical than a one-time pad?

I am experiencing confusion regarding one-time pads. I have read that a one-time pad generates a key that has the same length as the plaintext. This is considered to be an overhead in sharing such a ...