Cryptography on Karpoke - Just Another Blog

Demystifying SSH Key Types: From RSA to Ed25519

Thu, 24 Jul 2025 15:10:10 +0100

Explore SSH key types—RSA, DSA, ECDSA, Ed25519—and learn their pros and cons, best‑practice generation commands, and how to choose the right key for your needs.

» hackernoon.com | hackernoon.com

Un coloso de la informática

Sat, 15 Jun 2024 22:06:57 +0100

Tommy Flowers fue el primero al que se le ocurrió que podían fabricarse máquinas de computación completamente electrónicas

» César Tomé | culturacientifica.com

El algoritmo de cifrado DES explicado visualmente paso a paso

Mon, 15 Apr 2024 17:54:46 +0100

Esta detallada Explicación visual del algoritmo DES (Data Encryption Standard) es un curioso documento histórico, porque aunque el DES ya no se suele utilizarse por considerarse inseguro, muestra cómo funciona paso a paso en sus diferentes fases y operaciones. Tan educativo…

» @Alvy | microsiervos.com

What Is Encryption? — 6 Top Types of Encryption Methods + Examples

Sun, 18 Sep 2022 08:05:37 +0100

What Is Encryption? — 6 Top Types of Encryption Methods + Examples

» wazobia.tech | wazobia.tech

El algoritmo SHA-256 explicado y visualizado paso a paso, bit a bit

Sun, 27 Feb 2022 15:03:26 +0100

Esta maravilla creada por Domingo Martín llamada simplemente El Algoritmo SHA256 Explicado muestra cómo funciona exactamente el SHA-256, un algoritmo que se corresponde con la función hash criptográfica de 256 bits del Secure Hash Algorithm 2, creada por la NSA (Agencia…

» @Alvy | microsiervos.com

¿Qué es el protocolo de conocimiento cero?

Tue, 03 Aug 2021 14:01:22 +0100

Uno de los objetivos más buscados en Internet es el anonimato seguro. De la búsqueda de este principio nace el protocolo de criptografía conocido como ZKP (Zero Knowledge Proof) o prueba de conocim…

» Una Al Día | unaaldia.hispasec.com

Criptógrafos vulneran el protocolo de cifrado de Telegram

Wed, 21 Jul 2021 08:03:52 +0100

Hace unos días, un grupo de criptógrafos internacionales descubrieron cuatro vulnerabilidades asociadas al protocolo de cifrado de una de las aplicaciones de mensajería instantánea más populares de…

» Una Al Día | unaaldia.hispasec.com

All about HTTPS (part-2)

Sun, 11 Jul 2021 10:37:50 +0100

Encryption Keys Welcome to the second post of the series on All about HTTPS. In the prev…

» DEV Community | dev.to

TLS, SSL, HTTPS, CA, Encryption & MITM attack !

Sun, 24 Jan 2021 14:12:49 +0100

None of the above words have to make sense to you just yet. Go and grab a 🍺, give a HUGE ❤️ and smas…

» DEV Community | dev.to

[PoC] Cifrado AES256 mediante audio: AESTube (Parte 2)

Sun, 01 Nov 2020 16:34:18 +0100

Una vez diseñado el algoritmo que me permitía procesar el audio para obtener las notas, la idea era usarlas como passphrase del algoritmo de cifrado

» flu-project.com | flu-project.com

[PoC] Cifrado AES256 mediante audio: La Teoría

Thu, 01 Oct 2020 07:56:45 +0100

Todo empezó con una idea que llevaba tiempo rondándome la cabeza

» flu-project.com | flu-project.com

Two Lines of Code to Bulletproof Encryption: Advancements in Cryptography Development in the Wolfram Language

Wed, 17 Jun 2020 15:33:15 +0100

Cryptography functionality in the Wolfram Language supports generation and verification of digital signatures for expressions, files and cloud objects. Encrypt or digitally sign anything—from simple messages to images or code.

» Diego Olvera | blog.wolfram.com

La disección de un certificado TSL/SSL

Sat, 09 May 2020 15:00:11 +0100

Los certificados TSL, anteriormente conocidos como certificados SSL son otra forma de llamar a los certificados de clave pública X.509. Julia Evans ha hecho una gran labor explicando en su blog cómo es uno de estos certificados «por dentro» de forma…

» @Alvy | microsiervos.com

10 libros de seguridad informática para regalar estas navidades

Fri, 22 Dec 2017 11:10:00 +0100

Llegan las navidades, aunque comercialmente ya empezaron hace casi un mes, y que mejor que dar ideas para regalar o ser regalado. ¿No sabes que encargarle a los reyes magos? No te preocupes, vamos a comentar los 10 libros de seguridad informática que más leemos en Hispasec. Esos que yacen desgastados en los escritorios de auditoría, malware o el equipo 24x7 de Antifraude, nuestros incansables vigilantes. Leer y hacer son dos palabras claves en la construcción de un buen profesional, sea de la rama que sea. La formación es importante y una de las cosas que siempre ha estado presente en Hispasec es que el personal no le falte lectura, alimento para el cerebro.

How Dropbox securely stores your passwords

Sat, 24 Sep 2016 13:32:00 +0100

It’s universally acknowledged that it’s a bad idea to store plain-text passwords. If a database containing plain-text passwords is compromised, user accounts are in immediate danger. For this reason, as early as 1976, the industry standardized on storing passwords using secure, one-way hashing mechanisms (starting with Unix Crypt). Unfortunately, while this prevents the direct reading of passwords in case of a compromise, all hashing mechanisms necessarily allow attackers to brute force the hash offline, by going through lists of possible passwords, hashing them, and comparing the result. In this context, secure hashing functions like SHA have a critical flaw for password hashing: they are designed to be fast. A modern commodity CPU can generate millions of SHA256 hashes per second. Specialized GPU clusters allow for calculating hashes at a rate of billions per second.

Stealing Keys from PCs using a Radio: Cheap Electromagnetic Attacks on Windowed Exponentiation

Thu, 25 Jun 2015 22:16:00 +0100

We demonstrate the extraction of secret decryption keys from laptop computers, by nonintrusively measuring electromagnetic emanations for a few seconds from a distance of 50 cm. The attack can be executed using cheap and readily-available equipment: a consumer-grade radio receiver or a Software Defined Radio USB dongle. The setup is compact and can operate untethered; it can be easily concealed, e.g., inside pita bread. Common laptops, and popular implementations of RSA and ElGamal encryptions, are vulnerable to this attack, including those that implement the decryption using modern exponentiation algorithms such as sliding-window, or even its side-channel resistant variant, fixed-window (m-ary) exponentiation. We successfully extracted keys from laptops of various models running GnuPG (popular open source encryption software, implementing the OpenPGP standard), within a few seconds. The attack sends a few carefully-crafted ciphertexts, and when these are decrypted by the target computer, they trigger the occurrence of specially-structured values inside the decryption software. These special values cause observable fluctuations in the electromagnetic field surrounding the laptop, in a way that depends on the pattern of key bits (specifically, the key-bits window in the exponentiation routine). The secret key can be deduced from these fluctuations, through signal processing and cryptanalysis.

Attack of the week: FREAK (or ’factoring the NSA for fun and profit’)

Thu, 05 Mar 2015 22:19:00 +0100

A group of cryptographers at INRIA, Microsoft Research and IMDEA have discovered some serious vulnerabilities in OpenSSL (e.g., Android) clients and Apple TLS/SSL clients (e.g., Safari) that allow a ’man in the middle attacker’ to downgrade connections from ’strong’ RSA to ’export-grade’ RSA. These attacks are real and exploitable against a shocking number of websites – including government websites.

» Matthew Green | blog.cryptographyengineering.com

Secure Secure Shell

Tue, 06 Jan 2015 19:09:00 +0100

Reading the documents, I have the feeling that the NSA can 1) decrypt weak crypto and 2) steal keys. Let’s focus on the crypto first. SSH supports different key exchange algorithms, ciphers and message authentication codes. The server and the client choose a set of algorithms supported by both, then proceed with the key exchange. Some of the supported algorithms are not so great and should be disabled completely. If you leave them enabled but prefer secure algorithms, then a man in the middle might downgrade you to bad ones. This hurts interoperability but everyone uses OpenSSH anyway.

POODLE attacks on SSLv3

Fri, 14 Nov 2014 15:24:00 +0100

My colleague, Bodo M¶ller, in collaboration with Thai Duong and Krzysztof Kotowicz (also Googlers), just posted details about a padding oracle attack against CBC-mode ciphers in SSLv3. This attack, called POODLE, is similar to the BEAST attack and also allows a network attacker to extract the plaintext of targeted parts of an SSL connection, usually cookie data. Unlike the BEAST attack, it doesn’t require such extensive control of the format of the plaintext and thus is more practical. Fundamentally, the design flaw in SSL/TLS that allows this is the same as with Lucky13 and Vaudenay’s two attacks: SSL got encryption and authentication the wrong way around – it authenticates before encrypting.

How crackers ransack passwords like ’qeadzcwrsfxv1331’

Sat, 08 Jun 2013 23:06:00 +0100

In March, readers followed along as Nate Anderson, Ars deputy editor and a self-admitted newbie to password cracking, downloaded a list of more than 16,000 cryptographically hashed passcodes. Within a few hours, he deciphered almost half of them. The moral of the story: if a reporter with zero training in the ancient art of password cracking can achieve such results, imagine what more seasoned attackers can do.

Imagine no more. We asked three cracking experts to attack the same list Anderson targeted and recount the results in all their color and technical detail Iron Chef style. The results, to say the least, were eye opening because they show how quickly even long passwords with letters, numbers, and symbols can be discovered.

El cifrado sin control, no sirve de nada

Tue, 05 Mar 2013 15:23:00 +0100

Últimamente, tanto en auditorías que realizamos, como en código que encuentro en la red, hay una cosa que me llama poderosamente la atención, y es el mal uso (o uso incompleto) de las funciones de criptografía. Por lo general, el procedimiento que suelen seguir los desarrolladores que no están en contacto con el mundo de la seguridad, suelen consistir en coger un método que venga con la API del lenguaje o en una librería de terceros, buscar el método que implementa el algoritmo de cifrado de turno, rellenar la firma del método y almacenar la salida.

WhatsApp is using IMEI numbers as passwords

Fri, 07 Sep 2012 10:56:00 +0100

As you probably already heard in recent news, 1,000,001 Apple UDID’s were leaked. It’s unfortunate that so many apps use UDID’s to identify users since it’s extremely insecure.

This brings me to WhatsApp, a free messaging service, used by millions of people. Their system runs on a modified version of XMPP (Extensible Messaging and Presence Protocol). There is nothing wrong with using XMPP, but there is a problem in how WhatsApp handle authentication.

If you installed WhatsApp on an Android device for example, your password is likely to be an inverse of your phones IMEI number with an MD5 cryptographic hash thrown on top of it (without salt).
md5(strrev(’your-imei-goes-here’))

Decipher MPPE by breaking MS-CHAP v2

Mon, 20 Aug 2012 19:13:00 +0100

Our investigation focuses on Microsoft proprietary protocols with the help of a network trace and references. The steps that will be covered are specific to authentication view (MS-Chapv2), key derivation for encryption and the algorithm of the compression feature (MPPE/MPPC). Finally, to complete our approach, we will illustrate weaknesses through a new forensic tool dedicated to these protocols.

Mainline :

Details on MSChap-v2 : The first chapter aims to understand how the authentication protocol works ; Overview of MPPE protocol : We explain briefly the encryption protocol ; Overview of MPPC protocol : Here, we take a look at the compression feature ; Decipher MPPE by breaking MSCHAP-v2 : We decipher MPPE protocol with the help of MSChap-v2;

So You Want to Be a Security Expert

Tue, 24 Jul 2012 20:51:00 +0100

I regularly receive e-mail from people who want advice on how to learn more about computer security, either as a course of study in college or as an IT person considering it as a career choice.

First, know that there are many subspecialties in computer security. You can be an expert in keeping systems from being hacked, or in creating unhackable software. You can be an expert in finding security problems in software, or in networks. You can be an expert in viruses, or policies, or cryptography. There are many, many opportunities for many different skill sets. You don’t have to be a coder to be a security expert.

In general, though, I have three pieces of advice to anyone who wants to learn computer security.

Paper Enigma

Sun, 01 Jul 2012 21:02:00 +0100

Although the Enigma cipher as a whole is quite complex (it’s complexity is comparable to modern cryptographic algorithms) the individual transformations within it are relatively simple. In fact, they are simple enough that you can decipher an Enigma message with just a paper model. Our model is three-dimensional, to illustrate the wiring of a real Enigma machine. It needs only common household items to construct, and is completely compatible with all settings of a real Enigma machine (models I, M1, M2 and M3).

Why you should never use hash functions for message authentication

Wed, 27 Jun 2012 23:54:00 +0100

The general thrust of this post is: use a MAC function like HMAC to sign data, don’t use hash functions. Although not all hash functions suffer from the problem I’m going to illustrate, in general using a hash function for message authentication comes with a lot of potential problems because those functions aren’t designed for this task. You shouldn’t try to work around it by creatively processing the inputs or inventing some fancy way of chaining hash functions. Just use the functions that were designed for this task instead of inventing your own crypto schemes.

Actualización automática ¿Bendición o condena?

Tue, 26 Jun 2012 12:48:00 +0100

El caso TheFlame ha promovido muchas reacciones: los articulistas rellenan páginas con prefijos ”ciber” y la palabra ”guerra”. Las casas antivirus lo usan como arma de venta (aun sin haberlo detectado en cinco años) y Microsoft queda en evidencia con su PKI y la refuerza. TheFlame ha minado también la confianza: en los gobiernos, en los antivirus… pero sobre todo, en la criptografía y en la actualización automática.

» hispasec.com

Basics of Computational Number Theory

Wed, 16 May 2012 23:58:00 +0100

This document is a gentle introduction to computational number theory. The plan of the paper is to first give a quick overview of arithmetic in the modular integers. Throughout, we will emphasize computation and practical results rather than delving into the why. Simple programs, generally in JavaScript, are available for all of the algorithms mentioned. At the end of the paper we will introduce the Gaussian Integers and Galois Fields and compare them to the modular integers. Companion papers will examine number theory from a more advanced perspective.