RSA Key Vs. DSA Key
In the world of asymmetrical key cryptography, two of the predominant algorithms are RSA and DSA. Both systems require users to generate a keypair, a public key and a private key. However, these two encryption algorithms have different limits on the size of the keys users can generate and what encryption functions they can perform.
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Asymmetric Key Encryption
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RSA and DSA are two different algorithms for generating the keys for asymmetrical key encryption systems. These systems work by using two components: a public key and a private key. These take the form of two files that are generated at the same time and have unique file contents, but are mathematically linked to one another. The user who generates such a key distributes the public key to the general public, while making sure that he is the only one who can access the private key.
Whole Document Encryption
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When a user distributes his public key, anyone who has his public key can use it to encrypt a document. After the document is encrypted in this manner the only way to decrypt it is to use the public key's matching private key. Because the only one who has access to this private key is the user who distributed the public key, he is the only one who will be able to decrypt and access the document.
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File Signing
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The other function that asymmetrical key encryption can perform is to generate what are known as file signatures. These are used to certify that a file that a user is about to access has not been tampered with since the file's creation. By running the data which constitutes a given file and the contents of his private key through an asymmetrical file-signing program, the file's creator is left with an encrypted file-signature to distribute with his file. Anyone who has his public key can then use the same kind of software to check that the file's data has not been tampered with.
Which Algorithm to Choose
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When it comes to choosing whether you want to generate an RSA key or a DSA key, the primary difference is what encryption operations you wish to perform. RSA keys are capable of both whole document encryption and file signing. However, a DSA key is only used for signing documents. RSA allow users to generate key pairs whose sizes are larger than 1024 bits, which is the maximum size for a DSA key. As keys become more difficult to crack with increasing size, so the particularly security conscious should consider using RSA keys for their file signatures as well as whole document encryption.
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References
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