Description

The RtlSecureZeroMemory routine securely fills a block of memory with zeros in a way that is guaranteed not to be optimized away by the compiler.

Parameters

Ptr [in, out]

A pointer to the memory block to be securely filled with zeros.

cnt [in]

The number of bytes to fill with zeros.

Return value

RtlSecureZeroMemory returns a pointer to the memory block that was filled (Ptr).

Syntax

PVOID RtlSecureZeroMemory(
  [in, out] PVOID  Ptr,
  [in]      SIZE_T cnt
);

Remarks

• The function uses volatile memory accesses to ensure that the compiler cannot optimize away the zeroing operation, even if the memory appears to be unused after the call.

• This differs from RtlZeroMemory, which may be optimized away by the compiler if the memory is not accessed again.

• The function guarantees that all specified bytes will be set to zero and that this operation will not be removed by compiler optimizations.

Callers of RtlSecureZeroMemory can be running at any IRQL if the destination memory block is in nonpaged system memory. Otherwise, the caller must be running at IRQL <= APC_LEVEL.

Example

UCHAR SensitiveData[256];
UCHAR CryptographicKey[32];

// Use sensitive data
ProcessSensitiveInformation(SensitiveData);
PerformCryptographicOperation(CryptographicKey);

// Securely clear sensitive data from memory
// This will not be optimized away by the compiler
RtlSecureZeroMemory(SensitiveData, sizeof(SensitiveData));
RtlSecureZeroMemory(CryptographicKey, sizeof(CryptographicKey));

See also

RtlZeroMemory

RtlFillVolatileMemory

RtlSetVolatileMemory