Take the 2-minute tour ×
Cryptography Stack Exchange is a question and answer site for software developers, mathematicians and others interested in cryptography. It's 100% free, no registration required.

When we talk about nonce in Initialization Vector(IV), is it required to used numbers only? not any letters or special characters?

share|improve this question
An IV or nonce is a sequence of bytes, the concept of letters doesn't make much sense here. So what's your question? Are you talking about the ASCII representation of those bytes? Or the hex representation? –  CodesInChaos Jul 10 '12 at 11:30
It's just a string of bits, how you wish to interpret it is entirely up to you and irrelevant to the actual underlying cryptographic operations being performed (personally I like to use hex. representation for visual inspection as it's easy to compare bitwise, great for debugging) –  Thomas Jul 10 '12 at 11:40

1 Answer 1

up vote 3 down vote accepted

No. In the context of the Initialization Vector of a cipher operated in some mode, the most significant property of a cryptographic nonce is that it is not reused. It often matters that it is random and unpredictable (e.g. with CBC). It is immaterial that it represents a number or anything else under some particular encoding.

If an IV is chosen at random (which is standard, and best), it would be bad to restrict it to represent a number (say, restricting each byte to be a digit according to ASCII), in particular because it would dramatically increases the odds of reusing the same IV.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.