Reusing a Nonce, Key Pair in Encryption
Nonces should be used for the present occasion and only once.
Nonces are often bundled with a key in a communication exchange to produce a new session key for each exchange.
The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.
Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.
This code takes a password, concatenates it with a nonce, then encrypts it before sending over a network:
Because the nonce used is always the same, an attacker can impersonate a trusted party by intercepting and resending the encrypted password. This attack avoids the need to learn the unencrypted password.
This code sends a command to a remote server, using an encrypted password and nonce to prove the command is from a trusted party:
Once again the nonce used is always the same. An attacker may be able to replay previous legitimate commands or execute new arbitrary commands.
Weaknesses in this category are related to randomness.
Weaknesses in this category are related to the A02 category "Cryptographic Failures" in the OWASP Top Ten 2021.
Weaknesses in this category are related to the design and architecture of data confidentiality in a system. Frequently these deal with the use of encryption libraries....
This view (slice) covers all the elements in CWE.
This view contains a selection of weaknesses that represent the variety of weaknesses that are captured in CWE, at a level of abstraction that is likely to be useful t...
This view (slice) lists weaknesses that can be introduced during design.