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Questions tagged [hash-signature]

Hash-based digital signatures, such as Lamport one-time signatures, are digital signature schemes based on a (non-trapdoor) one-way function such as a cryptographic hash. Such schemes are expected to remain secure even against attacks using quantum computers.

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Advantages and disadvantages of hash-based signatures

We know hash-based signatures (Winternitz signature, HORS(T) signature) that are quantum-safe and efficient. They can be stateful or stateless, one-time or multiple-time. But why are they not widely ...
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Tuning the signature size of Sphincs+

If I only need a small number of signatures (perhaps $2^{10}$) for the lifetime of my key pair, how would I calculate the consequent signature size? Unfortunately managing state for an LMS or XMSS ...
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1answer
84 views

How secure is a hash based signature scheme after signing assuming quantum computers?

Consider a hash based signature scheme that requires taking the $k$-bit hash of an arbitrary length message to be signed (e.g. Lamport one-time signature scheme). My understanding is, assuming that ...
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Difference between XMSS and MSS-SPR

I am currently studying stateful hash based signatures. In the XMSS paper the authors claim that XMSS signatures are 4 times smaller than those of MSS-SPR. However I do not get how it is possible, ...
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1answer
137 views

How is SPHINCS Hash-based signature “stateless”?

I really hope someone can help me with these questions related to SPHINCS. I am trying to understand the concept of “stateless” vs. “stateful” signature scheme which is the basis of SPHINCS. I went ...
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Signing a message using SPHINCS Hash-based Signature scheme

I have questions on “SPHINCS: practical stateless has-based signature” by Bernstein et al. And I really hope that someone can help me with it. To help me understand it, I read the https://...
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23 views

How does the KeyGen of Merkle's improvement of Lamport's OTS work?

In his paper [1] on page 17 and 18, Merkle proposes an improvement on Lamport's OTS by only signing the 1's in the message in combination with a checksum of the amount of 0's in the message. I get the ...
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Are there any hash-based multisignature schemes?

Are there any hash-based signature schemes which would let two (or more) people sign the same message without increasing the size of the signature linearly? For my purposes, it is fine if the scheme ...
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1answer
51 views

In W-OTS, could you XOR all public keys?

Since the signatures all generate the public keys, those can be derived from sig and proven by pre-commited XOR of every pub key compared with XOR of every signature end hash.
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1answer
45 views

In W-OTS, is it trivial to forge smaller N values?

Just read about W-OTS, since the signature is the private key hashed 256-N times, is it trivial to forge a signature with a smaller vale for N when having access to original signature? I.e. just hash ...
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1answer
81 views

SPHINCS and HORST: can we sign the same message twice?

I was reading about SPHINCS which uses layers of WOTS+ trees and a bottom layer of HORST trees. HORST is a few time signature scheme, using a selection function you can sign at least twice without ...
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1answer
51 views

Basic question on hash-based signature scheme

If a hash-based signature schemes such as W-OTS is used, do we still need public key based certificates to prove ownership of a public key? I understand that hash-based signatures are one of the ...
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1answer
137 views

Does the One-Time Hash-based Signature Scheme render Ring Signatures useless?

On the Bitcoin community, to maintain privacy, they recommend using one-time spend addresses. CryptoNote, Monero et al. prefer Ring Signatures to maintain that privacy. There are some issues regarding ...
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1answer
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For a hash over a finite space without size reduction, is a public permutation sufficient?

Suppose the application is a Lamport signature scheme. Is the following a secure hash $\{0,1\}^n \rightarrow \{0,1\}^n$? $$ H(x) = x \oplus P(x) $$ where $P$ is a public permutation that permutes an ...
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Why does WOTS+ need a checksum during signing operation?

I was reviewing WOTS+ scheme for consideration in our private blockchain, and noticed that it had a small overhead of calculating a checksum as seen in the following pseudocode excerpt from the ...
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1answer
68 views

How many messages before Sphincs(+) becomes insecure?

How many messages would it take until the success probability of a forger becomes $1/2$? $1/4$?
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1answer
107 views

Why is WOTS-type signature schemes OTS?

I'm sure I've missed something super trivial, but why are WOTS-type schemes one-time? I've been looking into hash-based schemes, and I feel like I understand WOTS quite well (specifically I have ...
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Can this hash-based, short signature scheme work, given a decentralized log of messages as a primitive?

Suppose we had a decentralized log of messages, i.e., an ever-growing array of information on which anyone could append arbitrary data to. Given such primitive, could a party broadcast authenticated ...
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1answer
47 views

Convert a state-dependent hash-based signature scheme into a stateless message-dependent one

Suppose we have an XMSSMT instance that is capable of signing up to 2^60 messages securely when given some state-dependent information, I could envision making it stateless as follow: Hash the ...
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1answer
132 views

Bitmasks or seed along with public key in WOTS+ post-quantum signatures

The state of the art hash-based post-quantum signature schemes, like Sphincs and XMSS, are using variations of WOTS (Winternitz OTS), like WOTS+, that require extra random bitmasks along with the ...
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397 views

eXtended Merkle Signature Scheme (XMSS) vs Leighton-Micali Signature (LMS)

Very briefly, how does eXtended Merkle Signature Scheme (XMSS) stack up against Leighton-Micali Signature (LMS)? I'm asking this in the context of my article here.
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458 views

What are the advantages and disadvantages of Merkle signatures over Lamport signatures?

I know they are both hash-based and post-quantum secure, and that Lamport signatures can form the basis for a Merkle scheme, but what do you actually gain over standard Lamport signatures by doing ...
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1answer
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Smallest 256-bit security hash-based OTS?

What is the smallest hash-based OTS in terms of the sum of the public key and signature which provides 256 bits of security?
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361 views

How to use SPHINCS+?

Based on the NIST submission it looks like the SPHINCS+-256s algorithm comes in at public key sizes of 64 bytes, private key sizes of 128 bytes, and signature sizes ...
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548 views

Difference Between Gravity-SPHINCS and SPHINCS+?

What are the differences between Gravity-SPHINCS and SPHINCS+ from security and practicality standpoints? Are they just different implementations of the underlying SPHINCS algorithms or are they ...
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192 views

Blind Hash Signatures?

Is it possible to implement blind signatures with purely hash-based signature algorithms? Any whitepapers, code samples, etc on the subject would be helpful.
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1answer
220 views

What is a formal definition of strong one-time-secure signatures?

What is a formal definition of strong one-time-secure signatures? I know the Lamport's scheme is one of them, but what is the global definition of it?
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Sequential delayed release of chained HMAC keys for use as asymmetric signature

Iterative hashing of a private random seed can yield keys for use in HMAC, which if revealed publicly in reverse order and on predetermined schedule, can be used in a manner similar to other ...
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Winternitz One time signature security

There are two versions of Winternitz-One time signature scheme, $W-OTS$ and $W-OTS^+$ Security of both is as following $W-OTS$ is strongly unforgeable under chosen message attacks if $F$ is a ...
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563 views

Winternitz hash based signature signing and verification

In Winternitz hash based signature There are two functions $f: \{0,1\}^n \to \{0,1 \}^n$, a one way function and $g: \{0,1\}^* \to \{0,1 \}^n$, cryptographic hash function Key Generation steps ...
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395 views

Does still make sense to use SHA1?

I'm working with Arduino and hash-based signatures which are signature schemes that use only hash functions. Due to the constraints of an Arduino I was thinking about using SHA1 as the underlying ...
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1answer
464 views

How can I generate reasonably short temporary unlock codes?

I need a way to generate temporary unlock codes for an application to use when it can't go online to confirm that its activation subscription is still current. The application needs to able go ...
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3answers
880 views

Why do we need Collision Resistant Hash Function for the Merkle Tree Signature Scheme?

I am studying Merkle Tree Construction for digital signature. I don't quite understand why we need collision resistant hash function for Merkle tree construction. There are few papers like XMSS that ...
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Is there a signature scheme which doesn't rely on the difficulty of factoring/dlp which generates short signatures?

The Lamport signature scheme, for example, doesn't rely on the difficulty of any problem and it only depends on the existence of one-way functions. Is there an alternative scheme which also doesn't ...
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Why don't crypto-currencies use the Lamport signature scheme?

The Lamport signature scheme is faster, less complex and considerably safer than ECDSA. It's only downside - being only usable once - isn't really a downside when signing transactions, since you could ...
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1answer
118 views

Why are the bit lengths of keys and digests equal in Lamport signatures?

In Lamport's one time signature scheme: One way function to convert a pseudo random number private key to a public key takes $\{0,1\}^n$ and returns $\{0,1\}^n$. Cryptographic hash function to ...
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1answer
364 views

Do other one-time signature schemes exist?

I'm curious to know if there are any one-time signature schemes other than Lamport's or its variants (Merkle trees are one such variant). The first I've discovered is called "Bins and Balls" which ...
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2answers
776 views

Merkle signature scheme

I was browsing the Wikipedia article on Merkle signature schemes and noted that it says: The number of possible messages must be a power of two[…] Why is that? ...
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1answer
242 views

Choice of the one-way function (OWF) for Lamport signatures

I am studying the Lamport signature scheme, and I found that in many sources (eg: Hash-based Digital Signature Schemes) the input and output bitstring of the OWF and the message digest have the same ...
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1answer
179 views

Fast Forward Hash Signatures

As a follow up to the Q/A session: Small Quantum Signatures - Reality check needed I have implemented the discussed idea for a new short-quantum-safe signature system using fast-forwarding hash. It ...
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240 views

Small Quantum Signatures - Reality check needed

I've been thinking a bit lately about how to get quantum resistant signatures fast and (relatively) small. One idea I've been keen on exploring is finding a crypto PRNG that allows fast-forwarding, e....
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3answers
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Stateless hash based public key cryptography?

Merkle-Winternitz signatures based on fractal hash trees are an attractive alternative to other post-quantum cryptographic schemes, in particular since they are conceptually simple, the security ...
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1answer
965 views

Is ed25519 a “hash signature”

Writing my last question, I saw the hash-signature tag. I tried to research it best I could, but I'm simply overwhelmed in this field. I don't think it means to simply hash data before signing, but ...
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One-time digital signatures

Are there digital signatures for which, given two documents signed by the same key, one could derive the key? With such one-time signatures, one may be able to design a cryptocurrency based on proof-...
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Can one use a Cryptographic Accumulator to efficiently store Lamport public keys without the need of a Merkle Tree?

One of the problems of one-time Lamport signatures is that public keys are disposed after use, so you must generate many keys and store them in a Merkle tree. The root is the "real" public key and ...
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1answer
544 views

What is a Trapdoor in Merkle Signature?

Merkle signature (pag. 40) use than public key (verification key) the root of the Merkle Tree and than private key (to sign) the set of pre-images of the $g(Y_i)$ where $Y_i$ is the verification key ...
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Merkle Signature Generation

In the section 2 (page 42) of the book "Post Quantum Cryptography", it says: Then he generates the one-time signature $\sigma_{\text{OTS}}$ of the digest using the $s$-th one-time signature key $...
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545 views

Lamport-Diffie + Security Proof

I am studying Lamport-Diffie signature scheme. In the lecture present the algorithm $A'$ for attempting to invert the one way function $f$, where $f$ is used to compute the public key. My question is ...
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Lamport-Diffie + attempting to invert OWF

I am studying Lamport-Diffie signature scheme and in my lecture present the follow algorithm for attempting to invert the one way function $f$, where $f$ is used to compute the public key of this ...
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Winternitz One-Time Signature

I am reading the page 38 in this "Post Quantum Cryptography" book (Equations 8 and 9). My question is, why to compute the verification key $Y$, $f$ is applied $2^w-1$ times? Are there any security ...