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22

Yes, there are advantages to the attacker. Using a well vetted encryption algorithm provides a better assurance of security. There may be cryptographic algorithm flaws and/or coding mistakes. As noted, relying on the algorithm being private just adds a layer of false security.


8

The main advantage is that using a proprietary algorithm gives you access to trade secrets like additional cryptographic attacks that other algorithms fall to but to which the proprietary algorithm is resistant. Whether this is important depends on the amount of trust you have in the vendor. As other answers have noted, usually the staff of any one ...


8

The only advantage I can think of is that they're able to put "State of the art encryption" on their website. But even then, those with a trained eye may spot it as an issue, therefore rendering it as yet another disadvantage. But other than that pseudo-advantage, there are none. Chances are overwhelmingly good that this new cipher, having been ...


5

Custom crypto can be valuable when other aspects are more important than the confidentiality guarantee, and the well-known ciphers don't address those aspects. A custom cipher or custom application of a cipher would tend to offer a weaker guarantee of confidentiality than well-tested systems. But some users of encryption can handle an eventual breach so ...


4

Is there any problems from using the approach I am suggesting? Yes, there are several. First of all, some sites generate first time passwords, or even long time passwords. You may want to store those too. What if a site requires frequent updates? If one password is reversed, you'd still loose confidentiality. Would it actually be less secure if ...


4

The difference is: All SHA-0, 1 & 2 and MD5 come under a class of algorithm called Merkle–Damgård construction, while SHA-3 falls under Sponge functions. Merkle–Damgård construction is a method of building collision-resistant cryptographic hash functions from collision-resistant one-way compression functions. And, Sponge functions are a class of ...


3

Such a category of functions is not generally used as is, but compression functions, which are close to what you describe, are (as you describe) used to build (variable length) hash functions. For example, Merkle–Damgård hashes like SHA-2 have a compression function that takes an IV (or previous block output) and a fixed size data block to generate a smaller ...


2

There are several different scenarios to consider. If you assume all the sites/apps do things right, use a strong password hash, stay uncompromised, then no one should be able to find your master password anyway (unless it is a very poor low entropy password). So how or whether it is combined at all does not matter. More likely, you are interested in ...


2

A possible advantage is the need for cryptanalysis. Using only standard algorithms, an adversary who had a machine capable of breaking them could just feed your ciphertext into the machine. With a proprietary algorithm they would not have a ready-made machine for breaking it, so they would have to analyze it first, even if after that it would be very easy ...


2

The approach you describe is very much like the approach that is used in the masterpassword app (http://masterpasswordapp.com/). Roughly they generate a password for each site depending on: Your master password The site name A number (so that if you have to change your password you can just increase the number) Some salts that they decice. And then they ...


1

While Switch is right about the difference between Merkle–Damgård and Sponge constructions, I don't believe he is correct as to NIST's reasoning. I happened to talk to a NIST cryptographer (John Kelsey) about this. He indicated that they selected Keccak not because they distrust the SHA-2 design (Merkle–Damgård is provably secure if the compression ...


1

RIPEMD-160 uses precisely the same padding and endianess convention as MD5. Everything is little-endian, with the exception of the order of bits in bytes, which is kept big-endian. If the message is $n$-bit, it is appended a single bit at 1 and $511-((n+64)\bmod512)$ bit(s) at 0 , then the representation of $n$ on 64 bits. The resulting padded message is an ...


1

@Jeroba88 your idea of using a hash function rather than just appending the service name to your secret password is simple yet crucial to achieve what you have set off to do. Some level of customisation (be careful), such as using PBKDF2 (or Scrypt) in place of just a plain HASH(Password|Service) (especially since it's probably preferable to use ...



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