The OpenPGP encrypted data format (RFC 4880), and its implementations PGP and GnuPG.

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Why is padding the plaintext with a random string before encryption worse than OAEP / PKCS#7?

I'm reading about OAEP / PKCS padding used for PGP to turn deterministic algorithms like RSA from deterministic encryption to probabilistic encryption (randomness in the resulting output). That way ...
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Chosen Ciphertext Attack on the Public Key in PGP

In Secrets & Lies (2000), Schneier describes a chosen ciphertext attack on the public key under PGP: "Since RSA and ElGamal are malleable, known changes can be made to the symmetric key that ...
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39 views

Is a chosen ciphertext attack on PGP still possible?

In a paper from 2002 (pdf), Jallad et al describe a chosen ciphertext attack on PGP by taking advantage of the CFB mode that the block ciphers use under PGP. It's quite a devastating attack. Is this ...
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1answer
115 views

Using e-ID Number for Encryption and Digital Signing

I want to use e-ID number for performing Encryption/Decryption and Digital Signing - and in order to do so, I've opted a PGP-oriented approach which goes a bit like this. Generating PGP key-pair ...
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20 views

private-key can't be traced (GPG)?

I am very new to cryptography. I was reading about GPG/PGP Basics, and I have a doubt: As per my understanding, Everyone knows the algorithm (GPG) with which I generated my key pair. And If I give my ...
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93 views

Is this cascading encryption, and is my security weakened as a result?

I'm trying to understand what is, and what is not, considered cascading encryption. All of the posts and conversations I've read over the past few days discourage the practice, including this article. ...
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1answer
55 views

Encryption on the cloud with versioning

Can file-versioning, which is available for instance in Dropdox, weaken the security of encrypted files if someone is able to see two or more snapshots of the ciphertext at different times? To be ...
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2answers
267 views

PGP String-to-Key specifiers

I've been reading through the PGP Standard and here I'm a little confused. This section is discussing converting string data to a session key. I'm confused about the paragraph in bold. First off, what ...
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Initializing PGP keys by one side

I am using a PGP method to encrypt and decrypt messages shared between users A and B. Upon the start of a message exchange is the initialization of the public and secret keys by both Users. Lets say ...
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54 views

Why does “gpg --export-secret-keys” ask for a password?

What is it about the architecture of GPG that requires me to enter the password of the secret key when I export it with "gpg --export-secret-keys"? I would expect that gpg can just copy the relevant ...
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1answer
51 views

Can gnupg master key decrypt something encrypted with subkey?

When creating gpg subkeys, the master key signs and certifies that a subkey belongs to that master. That's ok, but, can master key decrypt something encrypted by a subkey? I guess no, but I want to be ...
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gnupg master key with certificate and authentication capabilities

After researching about GPG and Smartcards I came to a dilemma. The usual setup I've seen more widely is a master key (with SC capabilities) and 3 subkeys (with S, E, A each): ...
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A standard for multi-key provider encrypted data?

I'm looking for a standard that standardizes data encryption with multiple and diverse key sources to represent a heterogene access structure and culture. The standard must offer the following ...
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102 views

How to generate fingerprint for PGP public key

I would like to know how to generate a fingerprint for an openPGP public key. To be clear, I'm interested in how the fingerprint is generated. I'm aware that I can get the fingerprint with a ...
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1answer
116 views

How long can a RSA public key be?

If I create an RSA of 4096 bits, what would be the range of the length in bytes of the public key in DER format? Also, will the private key always be exactly 4096 bits (512 bytes)? Does the public ...
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506 views

OpenPGP Signature Packet hashed data

RFC 4880 describes the version 4 signature packet, tag 2, as ...
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142 views

Why does GPG ciphertext length differ with fixed plaintext length?

Thank you for your reply. Based on your inputs. I was investigated further, find details below Step 1) Input string for encryption is UUID format Input data = c0c6f311-a793-4d65-9374-1c0e45f5382c ...
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gpg 2048R - why encryption data length is different if text data 36 bytes

We are using gpg2 and base64 commands with 2048R algorithm Input: encrypted 36 bytes input text data with fixed length(36 bytes) current problem: if I run gpg command continuously, some times ...
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1answer
51 views

Perfect Forward Secrecy in PGP/asynchronous email

Looking at the RFC for PGP email/asynchronous chat with PFS here https://tools.ietf.org/html/draft-brown-pgp-pfs-03 can anyone tell me why the following scheme is no good? Alice and Bob retrieve each ...
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gpg --gen-random quality level: is higher “better”?

The GNU Privacy Guard manual pages have this to say about using the gpg --gen-random 0|1|2 count command: Emit count random bytes of the given quality level 0, ...
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Simplest way for strong cryptography in chat

I am a beginner in cryptography and I am interested for several weeks on this for my chat application. Basically, it is a centralized model. All messages are stored and potentially visible by ...
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1answer
188 views

Why does GnuPG save an array of remainders when generating prime numbers?

In looking at GPG's gen_prime() function, found within the cyphers/primegen.c file of ...
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1answer
134 views

ECDH and ECDSA in PGP with known public key

How are used ECDH and ECDSA in combination with public key ? Usually these methods are used for establish a secret themselves, ...
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1answer
107 views

OpenPGP Public-Key algorithm

What means when pgpdump shows this kind of algorithm in the Public-Key Encrypted Session Key Packet? ...
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Why are the first few bytes of a gpg encryption always the same?

If I run the command 'gpg -a -e < input.txt > output.txt' with completely different inputs (e.g. from /dev/urandom), the first 19 characters are always the same. What is this header? Is it ...
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184 views

Assemble RSA keys from components [closed]

I'm studying openpgp cryptography and struggling to understand some things. I can't use pgp tool for generating keys and ecryption, but have to write a simple app to generate keys, encrypt and decrypt ...
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1answer
34 views

Possible to detect if a message is PGP encrypted/signed (ciphertext)

Let's say I have a text field somewhere (i.e. an interactive user submitted text field on a PHP script, or a console application. Basically anything that accepts user input.) How can I detect if said ...
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365 views

Why must we generate the signature before any compression being done at PGP?

I have done some research on PGP and I found out there are of two reasons why we must generate the signature before doing any compression. Yet, I am not sure I really understand them both. One ...
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Details related to the ZIP algorithm used in PGP message encryption? [closed]

I am very new to PGP. PGP encryption works with hash function, asymmetric encryption, symmetric encryption and a zip algorithm (LZ77). What I know is that the zip algorithm is used to reduce the ...
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1answer
2k views

PGP public RSA key format

I have been trying to use Go (I could post the code, but I think I posted enough already...) to generate a PGP RSA key. However every time I try to encrypt something with it, something fails. However, ...
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1answer
100 views

Implementing forward secrecy in OpenPGP with public key authentication

I am trying to consider the feasibility of implementing an encrypted file sharing system, which both provides forward secrecy but also allows public key verification. I am stuck on the marriage ...
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1answer
155 views

Generating PGP key *without* random generator? (using fixed input only)

I understand why in general, a strong random generator or source of entropy is used when generating PGP keys. However, I have a use case where I want to generate PGP keys deterministically, i.e. ...
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1answer
419 views

Difference RSA keypair creation openSSL and openPGP?

Creating a 2048bits RSA keypair I figured that doing this using openssl takes as an input 32bytes of "randomness" from ...
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2answers
1k views

GPG/PGP Verification of Revocation

How does one verify a key revocation? After revoking a key and sending the revocation to MIT's keyserver, I noticed that the key is listed as such: ...
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378 views

Supersingular Isogeny Key Exchange Software [closed]

Are there any optimised implementations of the Supersingular Isogeny Key Exchange by Defeo, Jao, and Plut. It seems like this would be a great drop-in replacement for Diffie-Hellman in both OpenSSL ...
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3answers
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Some doubts about GnuPG

I've reading on GPG since yesterday and I have a doubt: the whole system of double key encryption does make sense but it looks to me like either way you are compromising something in terms of ...
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2answers
299 views

How to decrypt a PGP message with only the two primes and the public exponent?

I'm trying to decrypt a PGP Message that is encrypted with an RSA key, but I only have this information: Public exponent: 65537 Prime 1: ...
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2answers
598 views

PGP digital signature vs SHA256 HMAC Comparison

First let me admit that I am not a mathematician or a cryptographer. I am responsible for assisting in making a recommendation on a project that is consolidating payment processes within a company's ...
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1answer
77 views

Is it a bad idea to use PGP encryption for structured/predictable data?

I'm working on an app and need to encrypt some structured data. The data will be turned into a string form (JSON) before getting encrypted. The data format I'm using will always start with a ...
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1answer
96 views

How do revocation certificates work in PGP?

I've already read how to build and upload them, but I'm wondering how revocation certificates work, what informations they hold and so on. Suppose my private key is compromised, but I have a ...
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1answer
5k views

How to decrypt a '.enc' file that has been encrypted with RSA using a public key? [closed]

While solving a CTF challenge online, I came across a situation where I needed to decrypt a '.enc' file that has been encrypted using someone's public key. The ...
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1answer
136 views

How are RSA and ElGamal compatible in PGP?

I'm starting to play with PGP and I don't understand how if your key pair is RSA you can encrypt a message for someone whose key is for example ElGamal. How does the asymmetric key exchange work if ...
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1answer
502 views

How do you break encryption on a message? [closed]

This may seem like a simple question, but I have just started studying cryptography and I can't seem to find any information on this at all. I am trying to write a "simple" encrypted messenger using ...
4
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2answers
381 views

Signing Files vs. Signing File Hashes

What are the security pitfalls that may occur by signing a list of file hashes, versus signing individual files? In short, the security trade-offs between: ...
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0answers
90 views

What do you think about this message encryption?

I am currently working on my diploma project, a high security NFC door lock and need to exchange very sensible data. That's why I thought of PGP encryption, which is as far as I know one of the ...
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1answer
176 views

How exactly to extract information base 10 from a PGP RSA key pair?

I think I understand the mathematics of RSA ok. I'm not so computer savvy though. How, exactly, can I extract $n$, $e$, $d$, $p$ and $q$ from a PGP RSA public key pair? Is there like a converter ...
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1answer
2k views

Is it possible to determine a PGP public key from encrypted data?

Is it possible to find out which public key was used to generate the message? Scenario is like this : I got data which is encrypted with a public key. Now a "bad guy" hast the encrypted data, and ...
7
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1answer
1k views

How does GPG verify succesful decryption?

How does GPG (or other programs using the OpenPGP file format) verify that it has succeeded with decryption (for symmetrically encrypted data)? Is something appended to the clear text so there exist ...
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1answer
276 views

GPG & Mcrypt - difference?

in short I'm learning GUI programming in python and thought it could be interesting to make a small GUI for symmetric encryption. Not being mad/mathematical/experienced (take your pick) enough to try ...
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2answers
630 views

Can you fake messages from recorded message-history?

Lets assume Eve has a lot of PGP conversation with Alice and records all those messages. Bob is also regularly communicating with PGP with Alice. If Bob doesn't care about not having a signature ...