Questions tagged [cryptography]

Cryptography is the collective term for algorithmic techniques used to secure data from unauthorized entities.

Modern cryptography refers to a field of applied mathematics whose purpose is to secure electronic data. At its simplest, cryptography takes input m and performs operations on it, returning result n. M will either be impossible to determine from n, or it will require knowledge of a secret key to determine m from n.

Building blocks of cryptography include:

  • Cryptographic Hash Functions

    • A hash function (not to be confused with a hash table) takes an arbitrary input and returns a fixed-length output in such a way that minute changes in input will almost certainly produce major changes in the output.
  • Block Ciphers

    • A block cipher takes input of a fixed length and renders it unreadable to anyone who does not have knowledge of a secret key.
  • Stream Ciphers

    • A stream cipher takes input of an arbitrary length and processes it with a pseudo-random keystream (a string of pseudo-random numbers initialized with a secret key) to render it unreadable without knowledge of the key.

Cryptography is used in such protocols as TLS, SSL, and SSH, and is the basis for any secure electronic activity.

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What is randomart produced by ssh-keygen?

When you generate a key, you get "randomart" from newer versions of OpenSSH. I am unable to find an explanation of why, and what I'm supposed to use it for. Generating public/private rsa key pair. The key fingerprint…
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How can I get a list of installed certificates on Windows?

I know I have some certificates installed on my Windows 7 machine. How can I see what they are, the nicknames they are known by, and browse detailed information (such as issuer and available usage)?
Tim Keating
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Can other people on an encrypted Wi-Fi AP see what you're doing?

If you connect to an open, unencrypted Wi-Fi access point, everything you do can be captured by other people within range. If you connect to an encrypted point, then people nearby can intercept what you're doing, but can't decrypt it. The person…
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GnuPG / OpenGPG: Recovering public key from private key

I know that the public SSH key can be recovered from the private using ssh-keygen -y. How can a (deleted) public key be recovered from the private key in GPG (preferably in a way that is OpenGPG compatible)?
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Human-readable dump of gpg public key

Is there some tool to write out the actual content of a GnuPG public key in a way a human can unserstand? I mean not only ascii-armor which a human can read and type, but something which really breaks down the data into large decimal numbers for the…
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How do I create an RSA public\private key pair in Windows?

How do I create RSA public\private key pair file in Windows?
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How to force gpg2 to use expired key?

$ gpg -ear XXXXXXX gpg: XXXXXXXX: skipped: unusable public key $ gpg --debug-ignore-expiration -ear XXXXXXXX gpg: Invalid option "--debug-ignore-expiration" How to encrypt? There are no updates for the key available from keyservers. Messages…
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Steganography software

Do you know some good (better if FOSS and cross-platform) steganography software that runs on GNU/Linux? The features I'm searching are: steganography software (better if FOSS and cross-platform) it must run on GNU/Linux must hide data inside…
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get x and y components of ec public key using openssl

I am generating a KeyPair for ECC from curve 'secp128r1' using openssl Steps I followed : first I generated a private key using the command openssl ecparam -genkey -name secp128r1 -noout -out private.pem then i viewed the corresponding public…
Dhruv Agarwal
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Why are there so many files in C:\ProgramData\Microsoft\Crypto\RSA\MachineKeys

I am running out of disk space on C:-drive. We see many (millions of) files in C:\ProgramData\Microsoft\Crypto\RSA\MachineKeys What are these files ? Why are so many files created? How can we prevent this from happening? Can these files be deleted?
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OpenSSL ECDSA sign and verify file

I would like to sign and verify a pdf with elliptic curve. I got some code but it dosen't work. Create private key: openssl ecparam -genkey -name secp384r1 -noout -out private.pem Create public key: openssl ec -in private.pem -pubout -out…
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How can I use GnuPG with ECDSA keys?

I'd like to generate an ECDSA (rather than RSA, DSA, or ElGamal) key using GnuPG, and use it as I might otherwise use an OpenPGP-compatible master key. I've read that gpg2has support for ECDSA keys, but I haven't been able to use that functionality.…
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What happens if the private key of a Certificate Authority(CA) like Verisign is leaked?

I was just wondering what will happen if the private key of a CA is leaked? Won't it be then possible to make fake certificates for any other website?
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How to install True Image on Windows XP?

I have 1 license of Acronis True Image 2011 for 1 PC. I had it previously installed on my Windows Vista machine and it was working. Now, I wanted to move it to a Windows XP machine, by uninstalling it from Vista and installing it on XP. Note: Unlike…
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Vim no longer prompts for encryption key when reading encrypted file; why not, and how can I get this restored?

I recently began using Vim to encrypt text files (by using the :X command and entering an encryption key at the prompt). As documented, Vim then prompts for that key when I reopen the file and decrypts the text. Today, I opened one of those…
Andy Mo
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