Re: Openssl api for signature verification using digest

[Linta Maria <lintamaria194@xxxxxxxxx>]

Thanks Nicola for the updates.

But I need to verify signature with hashed data or digest not with original message.

Is there any openssl API to implement that?

On Tue 28 Aug, 2018, 5:18 PM Nicola, <nic.tuv@xxxxxxxxx> wrote:

Hi!

I would suggest using the newer `EVP_DigestSign` interface.

You could find more documentation about it here: https://wiki.openssl.org/index.php/EVP_Signing_and_Verifying

Here is the relevant manpage: https://www.openssl.org/docs/man1.1.1/man3/EVP_DigestVerifyInit.html

Best regards, 

Nicola Tuveri 

On Tue, Aug 28, 2018, 14:09 Linta Maria <lintamaria194@xxxxxxxxx> wrote:

Hi All,

 

 

I have started using open ssl recently for implementing some cryptographic operation.

Now I want to implement signature verification by taking Signature and hashed data as input, but I am not able to get the proper API.

I have used below code, but it’s not working. Please help me to get the correct API.

 

 

#include <openssl/evp.h>

#include <openssl/rsa.h>

 

EVP_PKEY_CTX *ctx;

unsigned char *md, *sig;

size_t mdlen, siglen;

EVP_PKEY *verify_key;

 

/*

  * NB: assumes verify_key, sig, siglen md and mdlen are already set up

  * and that verify_key is an RSA public key

  */

ctx = EVP_PKEY_CTX_new(verify_key, NULL /* no engine */);

if (!ctx)

     /* Error occurred */

if (EVP_PKEY_verify_init(ctx) <= 0)

     /* Error */

if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0)

     /* Error */

if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0)

     /* Error */

 

/* Perform operation */

ret = EVP_PKEY_verify(ctx, sig, siglen, md, mdlen);

 

/*

  * ret == 1 indicates success, 0 verify failure and < 0 for some

  * other error.

  */

 

 

 

Best regards,

George Linta Maria

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