Using such hash functions allows passwords to be securely stored on a computer. Instead of storing the list of paired usernames and passwords, the server stores only the list of username/fingerprint pairs.
Today, someone came into the #unix channel on Freenode asking how they could extract the fingerprints out of the hosts in their /.ssh/known_hosts file. I didn't know, so I dug through the man page for ssh-keygen, and found this:
F Secure Freedome Keygen 13
Why are they hashed, I wondered? It didn't take long for me to realize that your known_hosts file might be accessible to everyone on the system. Because they too could run "ssh-keygen -lf known_hosts", they could see what hosts/IPs you've connected to, and use that against you. So, it makes sense to hash that information, if you really don't need it.
Notice the "HashKnowHosts yes" option? Yup, that's your culprit. Check on RHEL and Fedora, it's not even listed in the file. Of course, you can override this behavior by placing the configuration option in your "/.ssh/config" file. Also, if you're on a Fedora-based operating system, and you want to hash your hosts, you can make the change rather easy. According to the ssh-keygen man page:
Kid-RSA (KRSA) is a simplified, insecure public-key cipher published in 1997, designed for educational purposes. Some people feel that learning Kid-RSA gives insight into RSA and other public-key ciphers, analogous to simplified DES.[9][10][11][12][13]
To avoid these problems, practical RSA implementations typically embed some form of structured, randomized padding into the value m before encrypting it. This padding ensures that m does not fall into the range of insecure plaintexts, and that a given message, once padded, will encrypt to one of a large number of different possible ciphertexts.
Standards such as PKCS#1 have been carefully designed to securely pad messages prior to RSA encryption. Because these schemes pad the plaintext m with some number of additional bits, the size of the un-padded message M must be somewhat smaller. RSA padding schemes must be carefully designed so as to prevent sophisticated attacks that may be facilitated by a predictable message structure. Early versions of the PKCS#1 standard (up to version 1.5) used a construction that appears to make RSA semantically secure. However, at Crypto 1998, Bleichenbacher showed that this version is vulnerable to a practical adaptive chosen-ciphertext attack. Furthermore, at Eurocrypt 2000, Coron et al.[26] showed that for some types of messages, this padding does not provide a high enough level of security. Later versions of the standard include Optimal Asymmetric Encryption Padding (OAEP), which prevents these attacks. As such, OAEP should be used in any new application, and PKCS#1 v1.5 padding should be replaced wherever possible. The PKCS#1 standard also incorporates processing schemes designed to provide additional security for RSA signatures, e.g. the Probabilistic Signature Scheme for RSA (RSA-PSS).
Secure padding schemes such as RSA-PSS are as essential for the security of message signing as they are for message encryption. Two USA patents on PSS were granted (U.S. Patent 6,266,771 and U.S. Patent 7,036,014); however, these patents expired on 24 July 2009 and 25 April 2010 respectively. Use of PSS no longer seems to be encumbered by patents.[original research?] Note that using different RSA key pairs for encryption and signing is potentially more secure.[27]
The security of the RSA cryptosystem is based on two mathematical problems: the problem of factoring large numbers and the RSA problem. Full decryption of an RSA ciphertext is thought to be infeasible on the assumption that both of these problems are hard, i.e., no efficient algorithm exists for solving them. Providing security against partial decryption may require the addition of a secure padding scheme.[29]
As of 2020[update], the largest publicly known factored RSA number had 829 bits (250 decimal digits, RSA-250).[32] Its factorization, by a state-of-the-art distributed implementation, took about 2,700 CPU-years. In practice, RSA keys are typically 1024 to 4096 bits long. In 2003, RSA Security estimated that 1024-bit keys were likely to become crackable by 2010.[33] As of 2020, it is not known whether such keys can be cracked, but minimum recommendations have moved to at least 2048 bits.[34] It is generally presumed that RSA is secure if n is sufficiently large, outside of quantum computing.
In 1998, Daniel Bleichenbacher described the first practical adaptive chosen-ciphertext attack against RSA-encrypted messages using the PKCS #1 v1 padding scheme (a padding scheme randomizes and adds structure to an RSA-encrypted message, so it is possible to determine whether a decrypted message is valid). Due to flaws with the PKCS #1 scheme, Bleichenbacher was able to mount a practical attack against RSA implementations of the Secure Sockets Layer protocol and to recover session keys. As a result of this work, cryptographers now recommend the use of provably secure padding schemes such as Optimal Asymmetric Encryption Padding, and RSA Laboratories has released new versions of PKCS #1 that are not vulnerable to these attacks.
There are many details to keep in mind in order to implement RSA securely (strong PRNG, acceptable public exponent...) [46]. This makes the implementation challenging, to the point the book Practical Cryptography With Go suggests avoiding RSA if possible.
MEGA is a secure cloud storage service based in Auckland, New Zealand. Infamous hacker and internet entrepreneur, Kim Dotcom, originally founded the service to provide secure cloud storage with end-to-end encryption. The service is public source, so the source code for the service can be accessed and audited by any third party.
Since it was first launched in 2013, Kim Dotcom has parted ways with the company, after claiming that it was no longer secure. Mega Limited, MEGA's parent company strongly denies that this is the case, and there is no evidence to suspect Dotcom's rumors were true. The service is now used by 210m users globally, and it is a secure and reliable service that users love because of its generous 15 GB free plan.
MEGA is a popular secure cloud storage service that is currently used by approximately 150 million people. Its cloud storage is primarily designed to work as a web-based service, which means it is easy to store data online using the browser on any device. However, nowadays mobile apps are available for Android, iOS, and Windows phones. Extensions for popular browsers such as Firefox, Chrome, Safari, and Opera. And desktop versions for Mac and Windows exist.
Clicking on "Take me to my Cloud Drive" results in you being prompted to store a downloadable recovery key. The key will allow you to recover your account if you forget your password. If you are comfortable that you will never forget the password; you do not really need the key. However, you may want to store it somewhere securely (such as in a secure password manager) just in case.
Overall, this is definitely a service that is ideal for beginners looking for a secure cloud storage service that is compatible with all their devices, provides syncing, and permits file sharing without having to learn anything complicated.
MEGA extension will allow you to install MEGA into your browser. It will reduce loading times, improve download performance and strengthen security. Any MEGA URL will be captured by this extension and stay local (no JavaScript will be loaded from our servers). Secure auto-updates are provided thanks to cryptographic private key signing. ... MEGA is more secure using the extension(s) because the web resources (JS/html) are loaded locally from within the extension itself, and therefore that prevents any possible MITM attack. ... Another good reason to use MEGA extension is that it will allow you to transfer larger files within the browser. Otherwise, the internal memory provided by the browser is very limited for file transfers.
Mega is a secure cloud storage service that operates with zero-knowledge of people's encryption keys. In such a service all documents are encrypted locally using a key that is never shared with MEGA. As a result of retaining full control over the encryption of their data, users never need to worry about their data being intercepted in transit or while at rest.
All communication with MEGA servers is secured using TLS/SSL. We checked MEGA using Qualys SSL labs, and the service received an A- which is a pretty good score (and means that data should be secure in transit).
Files and folders are encrypted using a AES-128, which should be secure long into the future (using currently known methods). Post-download or upload integrity checking is done through a chunked variation of CCM.
When it comes to finding a password manager that is both secure but also user-friendly, the task is not always easy. However, due to the way that MEGA is put together, it really is a doddle to use. And, if you are one of those people who often need to share files with friends and family - MEGA really does make it extremely easy to do it both securely and privately.
On the other hand, the fact that people have had legitimate files flagged up as pirated content and deleted is quite concerning, especially if you rely on the service to securely store your valuable intellectual property (think digital artists, musicians, developers, videographers etc). 2ff7e9595c
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