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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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How do hashes really ensure uniqueness?

This might seem an impractical and unnecessary conversation, but I feel it's something I need to clarify. Especially, as I just got my first developer job in a blockchain startup. So hashes are said ...
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1answer
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What is the difference between signatures and VRF?

For example we have asymmetric signature scheme(RSA or ECC based) and VRF(also can be RSA/ECC based), both of them can be verified using public key of the signer/hasher and also are unique for each ...
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1answer
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Does “hash than sign paradigm” apply to ECDSA cryptography?

From wikipedia https://en.wikipedia.org/wiki/Digital_signature#How_they_work and other articles I see that: "There are several reasons to sign such a hash (or message digest) instead of the whole ...
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2answers
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Usability of padding scheme in blinded RSA signature?

In Wikipedia's article on Blind signature, in the section Dangers of blind signing which describes RSA blinding attack one reads the following This attack works because in this blind signature ...
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3answers
3k views

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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3answers
5k views

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 ...
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1answer
758 views

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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1answer
713 views

Hash collision resistance requirements for Lamport signatures

According to the original paper, Lamport one-time signature scheme uses two one-way functions: $F$ and $G$. The former one, $F$, is used to create a public key by hashing elements of the private key (...
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1answer
645 views

1024 RSA Hash Signature attack. Forge a valid signature

I have an RSA signature of 1024 bit where i know the following: Public modulus N Public exponent (0x03) Cypher message Summary: An MD5 hash is calculated from a collection of byte and is used as ...
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3answers
3k views

Lamport signature: How many signatures are needed to forge a signature?

Lamport signature: Signing the message Note that now Alice's private key is used and should never be used again. The other 256 random numbers that she did not use for the signature she must never ...
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2answers
230 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
865 views

Proof that a hash matches an encrypted file

Assume that Alice has a file $F$ which she is going to send, in encrypted form to Bob. Alice possesses $F$ and an encryption key $K$. She sends to Bob the encryption of $F$ using $K$, $E(F,K)$ as ...
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1answer
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Is this Bleichenbacher '06 style signature forgery possible? (Or more like, why isn't it?)

I assume that most of you know this, but just for the sake of context; Bleichenbacher's signature forgery (https://www.ietf.org/mail-archive/web/openpgp/current/msg00999.html) basically abuses ...
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1answer
3k views

Certificate signature with SHA-1 and RSA: where do 1888 bits come from?

Plenty of X.509 Certificates use "PKCS#1 SHA1 with RSA encryption" as the Certificate Signature Algorithm for generating a 2048-bit signature. The SHA-1 hash function generates a hash value of 160 ...
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2answers
164 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
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Forging RSA1024 signature with e=3 where hash is right justified

I am trying to understand (in the frame of exponent 3) how to calculate a "forgery" in the case where the desired result is: xxxxxxxxxxx[...]xxxxxxxxxxxxxxxxxxxxHHHHHHHHHHH[...]HHHHHHHH where HH = a ...
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1answer
519 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 ...