Definition

block cipher

A block cipher is a method of encrypting text (to produce ciphertext) in which a cryptographic key and algorithm are applied to a block of data (for example, 64 contiguous bits) at once as a group rather than to one bit at a time. The main alternative method, used much less frequently, is called the stream cipher.

So that identical blocks of text do not get encrypted the same way in a message (which might make it easier to decipher the ciphertext), it is common to apply the ciphertext from the previous encrypted block to the next block in a sequence. So that identical messages encrypted on the same day do not produce identical ciphertext, an initialization vector derived from a random number generator is combined with the text in the first block and the key. This ensures that all subsequent blocks result in ciphertext that doesn't match that of the first encrypting.

This was last updated in January 2006
Posted by: Margaret Rouse

Email Alerts

Register now to receive SearchSecurity.com-related news, tips and more, delivered to your inbox.
By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy

More News and Tutorials

Do you have something to add to this definition? Let us know.

Send your comments to techterms@whatis.com

There are Comments. Add yours.

 
TIP: Want to include a code block in your comment? Use <pre> or <code> tags around the desired text. Ex: <code>insert code</code>

REGISTER or login:

Forgot Password?
By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy
Sort by: OldestNewest

Forgot Password?

No problem! Submit your e-mail address below. We'll send you an email containing your password.

Your password has been sent to: