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diff --git a/src/lib/crypto/elgamal.h b/src/lib/crypto/elgamal.h
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+/*-
+ * Copyright (c) 2017-2022 Ribose Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef RNP_ELG_H_
+#define RNP_ELG_H_
+
+#include <stdint.h>
+#include "crypto/rng.h"
+#include "crypto/mpi.h"
+
+typedef struct pgp_eg_key_t {
+    pgp_mpi_t p;
+    pgp_mpi_t g;
+    pgp_mpi_t y;
+    /* secret mpi */
+    pgp_mpi_t x;
+} pgp_eg_key_t;
+
+typedef struct pgp_eg_signature_t {
+    /* This is kept only for packet reading. Implementation MUST
+     * not create elgamal signatures */
+    pgp_mpi_t r;
+    pgp_mpi_t s;
+} pgp_eg_signature_t;
+
+typedef struct pgp_eg_encrypted_t {
+    pgp_mpi_t g;
+    pgp_mpi_t m;
+} pgp_eg_encrypted_t;
+
+bool elgamal_validate_key(const pgp_eg_key_t *key, bool secret);
+
+/*
+ * Performs ElGamal encryption
+ * Result of an encryption is composed of two parts - g2k and encm
+ *
+ * @param rng initialized rnp::RNG
+ * @param out encryption result
+ * @param in plaintext to be encrypted
+ * @param in_len length of the plaintext
+ * @param key public key to be used for encryption
+ *
+ * @pre out: must be valid pointer to corresponding structure
+ * @pre in_len: can't be bigger than byte size of `p'
+ *
+ * @return RNP_SUCCESS
+ *         RNP_ERROR_OUT_OF_MEMORY  allocation failure
+ *         RNP_ERROR_BAD_PARAMETERS wrong input provided
+ */
+rnp_result_t elgamal_encrypt_pkcs1(rnp::RNG *          rng,
+                                   pgp_eg_encrypted_t *out,
+                                   const uint8_t *     in,
+                                   size_t              in_len,
+                                   const pgp_eg_key_t *key);
+
+/*
+ * Performs ElGamal decryption
+ *
+ * @param rng initialized rnp::RNG
+ * @param out decrypted plaintext. Must be capable of storing at least as much bytes as p size
+ * @param out_len number of plaintext bytes written will be put here
+ * @param in encrypted data
+ * @param key private key
+ *
+ * @pre out, in: must be valid pointers
+ * @pre out: length must be long enough to store decrypted data. Max size of
+ *           decrypted data is equal to bytes size of `p'
+ *
+ * @return RNP_SUCCESS
+ *         RNP_ERROR_OUT_OF_MEMORY  allocation failure
+ *         RNP_ERROR_BAD_PARAMETERS wrong input provided
+ */
+rnp_result_t elgamal_decrypt_pkcs1(rnp::RNG *                rng,
+                                   uint8_t *                 out,
+                                   size_t *                  out_len,
+                                   const pgp_eg_encrypted_t *in,
+                                   const pgp_eg_key_t *      key);
+
+/*
+ * Generates ElGamal key
+ *
+ * @param rng pointer to PRNG
+ * @param key generated key
+ * @param keybits key bitlen
+ *
+ * @pre `keybits' > 1024
+ *
+ * @returns RNP_ERROR_BAD_PARAMETERS wrong parameters provided
+ *          RNP_ERROR_GENERIC internal error
+ *          RNP_SUCCESS key generated and copied to `seckey'
+ */
+rnp_result_t elgamal_generate(rnp::RNG *rng, pgp_eg_key_t *key, size_t keybits);
+#endif