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

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Fix timestamp of self signature on PGP public key [closed]

I accidentally changed configuration of my pgp key while my system didn't have the correct clock. And I uploaded my key to key servers. Now every time I try to download my key from key servers or even ...
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277 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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Explanation of cryptographic terminology for newbies [closed]

I feel like I'm making a mountain out of a molehill here, but I have (what should be) a relatively simple project, but the terminology used all over the Internet is either too simple or too difficult ...
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52 views

Binary format of encrypted PGP private key?

Short Version of the Question: I would like to remove any predictable information from an encrypted private keys binary representation. Does anyone have a hint where the binary format for encrypted ...
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how to create and use sub keys with PGP? [migrated]

let's say i wish to have forward secrecy with PGP, that requires me to create multiple sub keys to be used and destroyed accordingly, how should i do it?
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119 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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1answer
25 views

Older key as PGP subkey?

Currently I have a 2048-bit PGP key. Suppose I create a new 4096-bit key. Can I add that old key as a subkey of this new one?
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3answers
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Is PGP's way of maintaining email security optimal? [duplicate]

I read a book called "computer networking: A top-down approach". It talked about how PGP creates an email message between Alice and Bob to maintain confidentiality, integrity, and authenticity. Let me ...
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Is there a way to turn a PGP key into its semi-prime counterpart?

From my understanding of PGP keys they use the RSA algorithms to encrypt/decrypt messages. So, I know that the RSA algorithms use a semi-prime number to encrypt/decrypt messages. So, what I was ...
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38 views

Why does OpenPGP encryption produce different ciphertexts from the same plain text?

With the same plain text to be encrypted and the same public key, OpenPGP tends to produce a different ciphertext every time I run the encryption operation. Why is this?
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Different kind of PGP keys or IDs, how to interpret them?

When people say "Here's my PGP key", they tend to come up with all sorts of different stuff. Sometimes they provide an 8-digit hexadecimal number, which seems to be a key ID (although I'm not sure). ...
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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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44 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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22 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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96 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
56 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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1answer
59 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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68 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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12 views

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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120 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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123 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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515 views

OpenPGP Signature Packet hashed data

RFC 4880 describes the version 4 signature packet, tag 2, as ...
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151 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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58 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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94 views

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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191 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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144 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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112 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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1k views

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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195 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
36 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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392 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
106 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
169 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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420 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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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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1answer
429 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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90 views

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 security....
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312 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
659 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
80 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 ...
2
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1answer
106 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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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 ...