EVP_PKEY_ENCRYPT(3) | Library Functions Manual | EVP_PKEY_ENCRYPT(3)

# NAME

`EVP_PKEY_encrypt_init`, `EVP_PKEY_encrypt` — encrypt using a public key algorithm

# SYNOPSIS

library “libcrypto”
`#include <openssl/evp.h>`

int
`EVP_PKEY_encrypt_init`(EVP_PKEY_CTX *ctx);

int
`EVP_PKEY_encrypt`(EVP_PKEY_CTX *ctx, unsigned char *out, size_t *outlen, const unsigned char *in, size_t inlen);

# DESCRIPTION

The `EVP_PKEY_encrypt_init`() function initializes a public key algorithm context using key ctx->pkey for an encryption operation.

The `EVP_PKEY_encrypt`() function performs a public key encryption operation using ctx. The data to be encrypted is specified using the in and inlen parameters. If out is `NULL`, then the maximum size of the output buffer is written to the outlen parameter. If out is not `NULL`, then before the call the outlen parameter should contain the length of the out buffer. If the call is successful, the encrypted data is written to out and the amount of data written to outlen.

After the call to `EVP_PKEY_encrypt_init`(), algorithm specific control operations can be performed to set any appropriate parameters for the operation.

The function `EVP_PKEY_encrypt`() can be called more than once on the same context if several operations are performed using the same parameters.

# RETURN VALUES

`EVP_PKEY_encrypt_init`() and `EVP_PKEY_encrypt`() return 1 for success and 0 or a negative value for failure. In particular, a return value of -2 indicates the operation is not supported by the public key algorithm.

# EXAMPLES

Encrypt data using OAEP (for RSA keys). See also PEM_read_PUBKEY(3) and d2i_X509(3) for means to load a public key. You may also simply set “eng” to `NULL` to start with the default OpenSSL RSA implementation:

    #include <openssl/evp.h>
    #include <openssl/rsa.h>

    EVP_PKEY_CTX *ctx;
    unsigned char *out, *in;
    size_t outlen, inlen;
    EVP_PKEY *key;
    /* NB: assumes that key, in, inlen are already set up
     * and that key is an RSA public key
     */
    ctx = EVP_PKEY_CTX_new(key, NULL);
    if (!ctx)
    	/* Error occurred */
    if (EVP_PKEY_encrypt_init(ctx) <= 0)
    	/* Error */
    if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_OAEP_PADDING) <= 0)
    	/* Error */

    /* Determine buffer length */
    if (EVP_PKEY_encrypt(ctx, NULL, &outlen, in, inlen) <= 0)
    	/* Error */

    out = malloc(outlen);

    if (!out)
    	/* malloc failure */

    if (EVP_PKEY_encrypt(ctx, out, &outlen, in, inlen) <= 0)
    	/* Error */

    /* Encrypted data is outlen bytes written to buffer out */

# SEE ALSO

EVP_PKEY_CTX_new(3), EVP_PKEY_decrypt(3), EVP_PKEY_derive(3), EVP_PKEY_sign(3), EVP_PKEY_verify(3), EVP_PKEY_verify_recover(3)

# HISTORY

`EVP_PKEY_encrypt_init`() and `EVP_PKEY_encrypt`() first appeared in OpenSSL 1.0.0 and have been available since OpenBSD 4.9.

June 8, 2025 | Debian