Questions tagged [one-time-password]

A one-time password is a password that is valid for only one session or transaction.

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Is a deterministic PRNG seeded by with cryptographic hash a secure basis for generating one-time passwords?

I am building a passwordless auth scheme, and would like to avoid storing temp passwords in memory, so I wanted to derive them rather than store them. A valid password looks something like 'amendable-...
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Create a TOTP for machines using HMAC or AES

I'm trying to create a sort of Time-based One Time Password (TOTP) where machines are involved (not humans). In this kind of TOTP the step is 15 minutes between one code to the next one and both ...
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Forgery attack on Poly1305 when the key and nonce reused

Introduction: I've tried to find how reusing one-time key compromises itself but only found information that it breaks the encryption entirely, it is written everywhere. But since no methods to reuse ...
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Forward secrecy in Merkle trees vs. hash chains

Say we have a one-time password authentication system that uses a Merkle tree. Assume that the secret keys are of the form {sk0, sk1, ..., sk7}, and at time ...
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Difference Between an Authentication Token and an OTP (One Time Password)

I would like to better understand why some people use the term One Time Password and other Authentication Token. I have noticed that in academic circles, there is a differentiation between ...
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OTP Scheme where only one party can generate the OTP, but both parties can verify it's validity

As far as I understand, OTP usually works on a superficial layer by having two parties both know of a key and then authenticate each other by sharing a hash of the key and some sort of counter (e.g. ...
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The security of adding random noise many time pad

In may application, I have a series of real number $\{v_1, v_2, \ldots, v_N\}, v_i\in\mathbb{R}$. To protect them, I add a random noise $r\in\mathbb{R}$ to each themselves like one-time-pad encryption ...
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145 views

Security Considerations in using SHA-1 for One Time Passwords

SHA-1 is considered broken. That's why I'm assuming that using SHA-1 for RFC2289 OTPs is broken as well. Is this assumption correct? Going further with this assumption using SHA-1 for RFC4226 HOTPs ...
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Counters in HOTP

In the HOTP (HMAC-based One-time Password) algorithm the client and the server can have different counter values. Es. if an attacker tries to crack the password with no success. How does HOPT deal ...
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What is / How would I calculate the number of bits(?) I need to make the probability of a collision very small?

If I wanted to create a TOTP-esque algorithm that generated a string n characters long, with each character being a base64 character, generated from a user secret <...
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Are ephemeral keys symmetric or asymmetric? [closed]

My question is: Are ephemeral keys symmetric or asymmetric? If symmetric, can ephemeral keys be created based on a (UserID || nonce)?
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One time code appended to password

Apologies in advance, I'm a beginner and my knowledge of terminology in this field probably reflects that. I have a question about one-time codes being used with passwords. What inspires me to ask ...
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277 views

Is it possible to use crib drag on base64 cipher text?

I am pretty new to the cryptography scene but I wanted to know if it is possible to use crib dragging on cipher text which doesn't contain words? This data would be encrypted using the same key with a ...
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Can modular multiplicative inverse be used to create a secure cipher?

Let $N$ be a large number; and $(e, d, N)$ be a secret-key; where $e$ is a one-time random factor, and large enough (say the more or less the same number of bits as $N$), where $e < N$ and $e * d \...
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Reversed One-Time-Password - generating secret server side

In our company we're thinking about a new auth scheme (not a 2FA!) where vault is secured by secret. User should be able to access the vault just by typing the One-Time-Password (OTP) into the webform....
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Does two-factor authentication require one time use of one of the factors?

Do we need one of the factors of two factor authentication to be one-time use? TOTP and password are considered two factor authentication, but does smart card and password also count as two-factor ...
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TOTP intermittently does not return the same code when generated within the same time step

So we have the need for using a TOTP to generate a code on the server to send to a mobile client, I have been testing code generation with the following 3 java repos: https://github.com/jchambers/...
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Security concern with TOTP

I am pretty new to cryptography and I have been studying up on TOTP (Time Based OTP) and while I have learnt how the computation works, I'm unable to figure out why using TOTP makes a system more ...
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Recommended way to Implement One Time Password?

I need help with the process/commands needed to implement the below functionality: I'm modeling an OTP System, in which the user would request an OTP and the app will send him one. Later the user ...
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842 views

Is key derivation of a token shared secret necessary for usage of token in TOTP as specified by RF6238?

TL;DR: Is it necessary to generate a 'random' key from a shared token secret string before putting it into a TOTP algorithm that follows the RFC 6238 specification? Or is it okay for me to put the ...
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263 views

Stateless user-generated one-time passwords

I've been working on my course project lately and got stuck with the problem which I reduced to the following abstract protocol: Alice generates an ID key and gives it to Bob. Bob generates some ...
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Need help to get correct TOTP [closed]

I am really confused and need help on this problem related to TOTP as specified in RFC6238 here: https://tools.ietf.org/html/rfc6238#section-1.2. So I am now given a task to implement the RFC6238 to ...
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Is there a perpetual 2-factor-authentication scheme that allows temporary password generation?

Recall that current forms of two-factor authentication (2FA) rely on: Something you know, i.e. your password Something you have, i.e. your one-time password (OTP) generator on a trusted device The ...
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Alternative for RFC 6238/4226 - one time password via SMS (single-factor authentication)

Currently we have implemented One Time Passwords (OTP) as second authentication which works well. We use TOTP - RFC 6238 Some clients would like to have a "sms only" login, so it's single factor ...
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What's the industry standard for verifying phone number ownership?

What's the industry standard for generating single-use SMS codes verifying phone number ownership? I'm currently evaluating two main alternatives, both based on sending a verification code to that ...
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One Time Password generation algorithm to ensure data/transaction integrity?

Here is my use case: A user is trying to transfer money to his friend's account. He enters transaction details on banking website. Bank receives it and then Bank sends transaction details (receiver ...
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571 views

Does Lamport's authentication scheme still work if the hash function is not collision-resistant?

Geology professor Peter McMenteur gets interested in Lamport’s authentication scheme. After a brief study, he claims that the scheme works even if the hash function is substituted by a function ...
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How do I pick variable length passwords uniformly at random?

How do I pick passwords uniformly at random when given a min and max length? It seems that if I first pick a random length, then choose random characters, this procedure will choose shorter length ...
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Possible to generate a one time secret which all nodes on the distributed network can know but cannot pre compute

I have a distributed P2P network. Everyday, I want each node to have a secret which is only valid for that day, while each of the other remaining nodes on the network will be able to calculate the ...
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166 views

Security analysis of this one time password based scheme for copy protection

Imagine such protocol. Client and server initially share secret K[0]. When client wants to contact server she sends server K[0] and her ID. Server accepts request, and generated new random K[1] and ...
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738 views

Which method to generate one time password?

I'm looking for a concrete algorithm to generate one time passwords. The situation is as follows: Alice and Bob exchanged a passphrase over a secure channel in the beginning. They want to ...
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218 views

How to store and use a Cryptographic Seed in a database [closed]

Companies such as Barclays use cryptographic seeds (for their PINsentry system), RSA do the same for RSA SecurID, but how do they safely secure the seeds in the database. With passwords you just hash ...
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921 views

Retrieve timestamp from TOTP value

TOTP (Time-based One-Time Password) as I understand is an algorithm that uses the current time as a variable along with a shared key to generate a secured token. Wiki page for reference: http://en....
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Complexity of verifying OTP secret

What is the minimum number of unique pairs of digests and inputs to a one-time pass needed to verify that a secret is equal to a ...
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285 views

Detect desynchronization in HOTP authentication [duplicate]

In HOTP authentication, is there a way for a system to detect that the token has been desynchronized? If so how does it know that the OTP was generated from a desynchronized (but valid) token and is ...
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AES and One Time Passwords

I have used AES to secure my short term wireless network(1 day lifetime). The same symmetric key is used for securing entire network traffic. is it possible to improve security with onetime password ...
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813 views

counter to indicate hotp count

I was trying to figure out how HOTP kept from wrapping over, when I saw this explanation of how it works, by Thomas Pornin [source]: The intended scenario is the following: the client has a ...
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680 views

Practical usage of S/KEY

The One-Time-Password (OTP) topic became quite popular in the recent years. But unlike the well-known HOTP and TOTP standards I haven't heard about any applications/systems implementing and using the ...
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623 views

OTP sequence uniqueness

Is it possible to use Time-based One Time Password (TOTP) algorithms to generate tokens from multiple channels (where a channel is defined as a "user" using a certain shared key $K_c$ for channel $c$),...
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Why not just generate random strings for one-time password (OTP)?

http://en.wikipedia.org/wiki/One-time_password#How_OTPs_are_generated_and_distributed Why have so many methods to generate OTPs, why not just use just random strings?
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Why are HOTP and TOTP implementations all using 6 digits and not more?

I was checking the RFC's after wondering for some time. In RFC 4226 - HOTP: An HMAC-Based One-Time Password Algorithm, it states on the appendix: A simple enhancement in terms of security would be ...
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561 views

How HOTP values are validated according to RFC 4226

In Section 7.2 "Validation of HOTP Values" of the HOTP spec (RFC 4226) it says, in part, The HOTP client (hardware or software token) increments its counter and then calculates the next HOTP ...
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How does SafeNet MobilePASS generate passwords?

We use MobilePASS at work but the latest version of the android client seems to be buggy so I wanted to have a go at implementing the algorithm myself. You can download the client to play with here: ...
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199 views

Why does the server in S/KEY authentication only store a single password?

I've been reading about the S/KEY One-Time Password system on wikipedia here and was wondering why the server only stores a single password and not the list of one-time passwords like the client does. ...
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Question about use of IV in this cipher

Main cipher objective : Generate a keyed CSPRN stream, that does not expose useful information about the state of the CSPRNG, and xor this with the plaintext. To prevent an attacked who could somehow ...
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RSA and One-time Password (OTP) service

What is the expert cryptographic opinion on the following? Assume that there is a web server and a Client on web page who calls an OTP ([One-Time Password]) web service on the server which: creates ...
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669 views

How do single use passwords work for an encrypted message

LastPass encrypts its data before sending it to their servers. The key for the data is generated using a combination of the master password and username. How then can a one-time password be used to ...
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Why does HOTP use such a complex truncate function?

In the HOTP protocol after calculating a 20 byte hash it is truncated to 4 bytes. For this first an offset is calculated (low-order 4 bits of the last byte) which determines the four bytes to be ...
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777 views

Is it considered insecure in an HOTP implementation to publicly provide the next counter?

I am working on a project that needs to securely authenticating one or more smartphone clients with a server running on a microcontroller so it has very limited resources. I have found plenty of ...
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Is TOTP or a timestamp encryption a better timestamp-based authentication token system?

Are there advantages to using TOTP over encrypting a timestamp with a shared secret, in cases where the readability or ease of typing the token are not important?