Nonce

As explained in Software Security for Developers

A nonce is a value intended to be used only once within a specified cryptographic or authentication context.

A nonce is a unique, random value intended for one use within a cryptographic or authentication context. It makes a request or encryption operation distinguishable and helps prevent replay. section 13.3.3 section 5.2.1

OIDC authentication

A client sends a nonce with an OIDC authentication request. When the ID token returns, it must contain the same nonce; a mismatch causes rejection and blocks reused authentication data. section 13.3.3

Keep these nearby distinctions in mind:

• Nonce limits replay by making authentication data valid only once; state instead links an authentication request to the client session and helps prevent CSRF. section 13.3.3
• In AES-CBC, the IV acts as a nonce: use a different IV for every encryption operation with the same key. section 5.2.1

Figure 13.8 Using a nonce with a properly signed transaction prevents hackers from replaying or modifying the request, ensuring the transaction is secure and unique.

Visualizes how a nonce supports a unique, properly protected transaction and blocks replay or modification. section 13.3.3

How Software Security for Developers covers it

How deep it goes

Defines nonce use, explains request-to-token matching and IV reuse risks, but defers the mathematics of encryption-mode consequences.

Examples

Uses OIDC authentication responses, intercepted payment requests, and AES-CBC encryption of multiple files.

What it assumes

Assumes basic authentication and encryption contexts while defining nonce terminology and its practical security purpose.

What you can do after

Apply it via OIDC validation and AES-CBC IV management to reject reused authentication data and avoid key-IV reuse.

How it connects

Connects nonces with OpenID Connect, ID tokens, replay attacks, CSRF, initialization vectors, and AES-CBC.

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Also explained in

• 

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  Real-World CryptographyA nonce is a value intended to distinguish cryptographic operations and, in signature generation, is typically required to be unique for each signature under a key.
• 

  liveBookmanning.com
  Building Web APIs with ASP.NET CoreA script nonce is a cryptographically unpredictable token that authorizes a specific inline script under a content security policy.
• 

  liveBookmanning.com
  Hacking CryptographyA cryptographic nonce is a value intended to be used once to prevent identical cryptographic inputs from producing repeated protected outputs.

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Related concepts

• ECDSAused by · ECDSA is a public-key digital signature algorithm that uses elliptic-curve arithmetic to generate and verify signatures.
• replay attackaddresses · A replay attack is an attack in which previously captured valid messages, requests, or authentication data are retransmitted to produce an unauthorized effect.
• initialization vectorincludes · An initialization vector is a typically nonsecret value supplied to a cryptographic operation to initialize or vary its processing across uses.
• Content-Security-Policyconfigures · Content Security Policy is a web security standard that lets a site specify browser-enforced rules restricting the sources and forms of content a document may load or execute.
• authenticated encryption with associated dataused by · Authenticated encryption with associated data is a cryptographic construction that encrypts plaintext while authenticating the ciphertext and optional unencrypted associated data.
• openid connectused by · OpenID Connect is an identity layer built on OAuth 2.0 that enables clients to authenticate end users and obtain standardized identity claims.

This explainer was generated by Manning's knowledge graph from the text of Software Security for Developers. The section links point to the parts of the book it draws on.