BCRYPT_PQDSA_PADDING_INFO structure

2025-07-22

Note

Some information relates to a prerelease product which may be substantially modified before it's commercially released. Microsoft makes no warranties, express or implied, with respect to the information provided here. The feature described in this topic is available in pre-release versions of the Windows Insider Preview.

The BCRYPT_PQDSA_PADDING_INFO structure is used to specify the padding scheme for Post-Quantum Digital Signature algorithms (PQDSA).

Syntax

typedef struct _BCRYPT_PQDSA_PADDING_INFO {
  PUCHAR    pbCtx;
  ULONG     cbCtx;
  LPCWSTR   pszPrehashAlgId;
} BCRYPT_PQDSA_PADDING_INFO;

Fields

pbCtx

A pointer to the buffer that contains the context string.

May be NULL. If pbCtx is NULL, then cbCtx must be set to 0.

cbCtx

The size, in bytes, of the context string pointed to by pbCtx. Its value must be 0 if pbCtx is NULL. Otherwise, it must be a non-zero integer less than 256.

pszPrehashAlgId

A CNG hash algorithm identifier. This parameter indicates whether the pure (e.g. ML-DSA) or the pre-hash (e.g. HashML-DSA) variant will be used. A NULL value indicates the use of pure variant. To use a pre-hash variant, this identifier must refer to an approved hash algorithm: SHA-2, SHA-3, or SHAKE.

Remarks

For many PQDSA signatures, the use of BCRYPT_PQDSA_PADDING_INFO is not required. Using NULL pPaddingInfo in calls to BCryptSignHash and BCryptVerifySignature is equivalent to using pure variant with an empty context string.

Requirements

Requirement	Value
Minimum supported client	Windows Insiders (build 27843): Support for ML-DSA begins. [desktop apps only]
Minimum supported server	Windows Insiders (build 27843): Support for ML-DSA begins. [desktop apps only]
Header	`bcrypt.h`

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