[openssl-users] Openssl api for signature verification using digest

[Linta Maria]

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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