Root > Reference > All Functions > RSAVerify

Function RSAVerify

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Verifies digital signature.

 

Unit

EEncrypt

 

Syntax

 

Code (Delphi)

function RSAVerify(

const AKey: TRSAKey;

const AData: Pointer;

const ADataSize: Cardinal;

const ASignature: Pointer;

const ASignatureSize: Cardinal

): Boolean; overload;

 

function RSAVerify(

const AKey: TRSAKey;

const AData: TEncryptBuffer;

const ASignature: TRSASignature

): Boolean; overload;

 

function RSAVerify(

const AKey: TRSAKey;

const AData: RawByteString;

const ASignature: TRSASignature

): Boolean; overload;

 

Parameters

AKey [in]

A key for verification. Comes from RSAGenKey function or RSALoadPublicKey function. Must match the key used in RSASign function to sign AData. A public key will be used.

 

AData [in]

Data to be verified (the same data as the one passed to RSASign function). Must be unmodified (otherwise function will return False).

 

ADataSize [in]

Size of AData in bytes.

 

ASignature [in]

Signature to be verified (the same signature as the one returned by RSASign function). Little-endian.

 

ASignatureSize [in]

Size of ASignature in bytes.

 

Return value

True - if digital signature is OK, False - if digital signature is broken (i.e. AData is not the same/was changed; or wrong key is used).

 

Remarks

This function verifies digital signature created by RSASign function.

 

Your public key will be used for verification.

 

Important!

The signature bytes must be in little-endian order. You must reverse bytes order (before calling RSAVerify) if you want to verify signature generated by other tools which produce big-endian order signatures (such as .NET or OpenSSL).

 

Examples

 

Code (Delphi)

var

// Key to verify

RSAKey: TRSAKey;

// Data to verify

S: String;

// Digital signature for S

Signature: TRSASignature;

// If signature is broken or not

SignatureOK: Boolean;

begin

// Load public key

RSAKey := RSALoadPublicKey('C:\Public.pem', rsText);

try

 

// Data to verify

// (same as in RSASign example)

S := 'Some data';

 

// Load signature

Signature.cbData := HexCalcDecodedSize(Length(edSignature.Text));

Signature.pbData := AllocMem(Signature.cbData);

try

Base64DecodeFromString(edSignature.Text, Signature.pbData);

 

// Verify signature

SignatureOK := RSAVerify(RSAKey, Pointer(S), Length(S) * SizeOf(Char), Signature.pbData^, Signature.cbData);

 

// Clear key as soon as possible

RSADestroyKey(RSAKey);

 

if SignatureOK then

 // OK for S = 'Some data'

 Application.MessageBox('OK', 'Signature verification', MB_OK)

else

 // FAIL for any other S

 Application.MessageBox('FAIL', 'Signature verification', MB_OK or MB_ICONSTOP);

 

finally

SecureFree(Signature);

end;

finally

RSADestroyKey(RSAKey);

end;

end;

 

See also



Send feedback... Build date: 2023-09-11
Last edited: 2023-09-11
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