The public key will be used to encrypt the files at the client side and the private key will be used to decrypt those files when they arrive at the server. For example, at the start of an SFTP session, the user can use his private key to "sign" at the client side. The managed file transfer server will then use the corresponding public key stored at the server side to verify the digital signature and, consequently, the user's identity.
If you want a more detailed discussion on server and client keys, I encourage you to read the article " Roles of Server and Client Keys in Secure File Transfers ".
Before I proceed, I'd like to point out that, given equal key lengths, the cryptographic strengths of these two algorithms are just about the same.
So if the strength of your encryption is all that matters to you, then there's no need to read the rest of this article.
You can pick a key algorithm randomly if you want. However, if performance is an issue maybe because you're using old machines or you simply have thousands of users simultaneously doing secure file transfers and there's really a need to eke out computing resources, then read on. The meaning of DSA should give you an idea what it is for or to be more accurate, what it was originally designed for. As its name implies, DSA was originally intended only for signing.
But now, it can be used for encrypting as well. RSA, on the other hand, has long been used for both encryption and signing.
Right now the question is a bit broader: RSA vs. DSA vs. ECDSA vs. A presentation at BlackHat suggests that significant advances have been made in solving the problems on complexity of which the strength of DSA and some other algorithms is founded, so they can be mathematically broken very soon. Moreover, the attack may be possible but harder to extend to RSA as well. The presentation suggests using elliptic curve cryptography instead. And if NSA can already crack it, then it won't be as hard to crack for somebody else as a proper curve would be.
Ed is the same thing but with a better curve, so it's the safest bet against the underlying algorithm being mathematically broken. In practice that means that if you connect to your server from a machine with a poor random number generator and e. With the advent of mobile devices being used for highly private transactions, more secure, low-overhead encryption schemes are becoming highly desirable.
ECC cryptography helps to establish a level security equal to or greater than RSA or DSA, the two most widely-adopted encryption methods — and it does it with less computational overhead, requiring less processing power, and moving well beyond the mobile sphere in implementation.
Submit your Question Close. SSL Brands. We promise 30 days replacement and refund policy. Domain Validation SSL. Diffie-Hellman: The first prime-number, security-key algorithm was named Diffie-Hellman algorithm and patented in Other Helpful Articles: Symmetric vs.
Asymmetric Encryption — What are differences? Digital Signature vs. What is a Certificate Authority CA? Start Securing Your Website Today! What would lead someone to choose one over the other? DSA is faster for signature generation but slower for validation, slower when encrypting but faster when decrypting and security can be considered equivalent compared to an RSA key of equal key length.
That's the punch line, now some justification. The security of the RSA algorithm is based on the fact that factorization of large integers is known to be "difficult", whereas DSA security is based on the discrete logarithm problem. Today the fastest known algorithm for factoring large integers is the General Number Field Sieve , also the fastest algorithm to solve the discrete logarithm problem in finite fields modulo a large prime p as specified for DSA.
Now, if the security can be deemed as equal, we would of course favour the algorithm that is faster. But again, there is no clear winner. You may have a look at this study or, if you have OpenSSL installed on your machine, run openssl speed. You will see that DSA performs faster in generating a signature but much slower when verifying a signature of the same key length. Verification is generally what you want to be faster if you deal e. The signature is generated once - so it's fine if this takes a bit longer - but the document signature may be verified much more often by end users.
Again you want decryption to be faster here because one encrypted document might be decrypted many times. Right now the question is a bit broader: RSA vs. DSA vs. ECDSA vs. A presentation at BlackHat suggests that significant advances have been made in solving the problems on complexity of which the strength of DSA and some other algorithms is founded, so they can be mathematically broken very soon. Moreover, the attack may be possible but harder to extend to RSA as well. The presentation suggests using elliptic curve cryptography instead.
And if NSA can already crack it, then it won't be as hard to crack for somebody else as a proper curve would be. Ed is the same thing but with a better curve, so it's the safest bet against the underlying algorithm being mathematically broken. In practice that means that if you connect to your server from a machine with a poor random number generator and e. In SSH, on the client side, the choice between RSA and DSA does not matter much, because both offer similar security for the same key size use bits and you will be happy.
When version 2 was defined, RSA was still patented, so support of DSA was added, so that an opensource patent-free implementation could be made. RSA patent expired more than 10 years ago, so there is no worry now. Theoretically, in some very specific situations, you can have a performance issue with one or the other: if the server is a very small machine say, an i , it will prefer clients with RSA keys, because verifying a RSA signature is less computationally expensive than verifying a DSA signature.
Conversely, a DSA signature is shorter typically 64 bytes vs so if you are very short on bandwidth you would prefer DSA. Anyway, you will have a hard time detecting those effects, let alone find them important. On the server , a DSA key is preferred, because then the key exchange will use a transient Diffie-Hellman key, which opens the road for "Perfect Forward Secrecy" i.
If one of those properties is violated, it's possible to trivially recover the private key from one or two signatures. With RSA, in those situations only your ephemeral session key would have been compromised, if the actual authentication key pairs have been created using a properly seeded PRNG before. OpenSSH 7. It too is weak and we recommend against its use.
The math might not matter. This thread seems pre-Snowden. Here is a Reuters article dated December 20, :. Reuters - As a key part of a campaign to embed encryption software that it could crack into widely used computer products, the U.
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