crypto: akcipher - Drop sign/verify operations

A sig_alg backend has just been introduced and all asymmetric
sign/verify algorithms have been migrated to it.

The sign/verify operations can thus be dropped from akcipher_alg.
It is now purely for asymmetric encrypt/decrypt.

Move struct crypto_akcipher_sync_data from internal.h to akcipher.c and
unexport crypto_akcipher_sync_{prep,post}():  They're no longer used by
sig.c but only locally in akcipher.c.

In crypto_akcipher_sync_{prep,post}(), drop various NULL pointer checks
for data->dst as they were only necessary for the verify operation.

In the crypto_sig_*() API calls, remove the forks that were necessary
while algorithms were converted from crypto_akcipher to crypto_sig
one by one.

In struct akcipher_testvec, remove the "params", "param_len" and "algo"
elements as they were only needed for the ecrdsa verify operation.
Remove corresponding dead code from test_akcipher_one() as well.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Lukas Wunner 2024-09-10 16:30:21 +02:00 committed by Herbert Xu
parent a16a17d3ea
commit 6b34562f0c
8 changed files with 65 additions and 284 deletions

View File

@ -11,7 +11,7 @@ Asymmetric Cipher API
:doc: Generic Public Key API
.. kernel-doc:: include/crypto/akcipher.h
:functions: crypto_alloc_akcipher crypto_free_akcipher crypto_akcipher_set_pub_key crypto_akcipher_set_priv_key crypto_akcipher_maxsize crypto_akcipher_encrypt crypto_akcipher_decrypt crypto_akcipher_sign crypto_akcipher_verify
:functions: crypto_alloc_akcipher crypto_free_akcipher crypto_akcipher_set_pub_key crypto_akcipher_set_priv_key crypto_akcipher_maxsize crypto_akcipher_encrypt crypto_akcipher_decrypt
Asymmetric Cipher Request Handle
--------------------------------

View File

@ -20,6 +20,19 @@
#define CRYPTO_ALG_TYPE_AHASH_MASK 0x0000000e
struct crypto_akcipher_sync_data {
struct crypto_akcipher *tfm;
const void *src;
void *dst;
unsigned int slen;
unsigned int dlen;
struct akcipher_request *req;
struct crypto_wait cwait;
struct scatterlist sg;
u8 *buf;
};
static int __maybe_unused crypto_akcipher_report(
struct sk_buff *skb, struct crypto_alg *alg)
{
@ -126,10 +139,6 @@ int crypto_register_akcipher(struct akcipher_alg *alg)
{
struct crypto_alg *base = &alg->base;
if (!alg->sign)
alg->sign = akcipher_default_op;
if (!alg->verify)
alg->verify = akcipher_default_op;
if (!alg->encrypt)
alg->encrypt = akcipher_default_op;
if (!alg->decrypt)
@ -158,7 +167,7 @@ int akcipher_register_instance(struct crypto_template *tmpl,
}
EXPORT_SYMBOL_GPL(akcipher_register_instance);
int crypto_akcipher_sync_prep(struct crypto_akcipher_sync_data *data)
static int crypto_akcipher_sync_prep(struct crypto_akcipher_sync_data *data)
{
unsigned int reqsize = crypto_akcipher_reqsize(data->tfm);
struct akcipher_request *req;
@ -167,10 +176,7 @@ int crypto_akcipher_sync_prep(struct crypto_akcipher_sync_data *data)
unsigned int len;
u8 *buf;
if (data->dst)
mlen = max(data->slen, data->dlen);
else
mlen = data->slen + data->dlen;
mlen = max(data->slen, data->dlen);
len = sizeof(*req) + reqsize + mlen;
if (len < mlen)
@ -189,8 +195,7 @@ int crypto_akcipher_sync_prep(struct crypto_akcipher_sync_data *data)
sg = &data->sg;
sg_init_one(sg, buf, mlen);
akcipher_request_set_crypt(req, sg, data->dst ? sg : NULL,
data->slen, data->dlen);
akcipher_request_set_crypt(req, sg, sg, data->slen, data->dlen);
crypto_init_wait(&data->cwait);
akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP,
@ -198,18 +203,16 @@ int crypto_akcipher_sync_prep(struct crypto_akcipher_sync_data *data)
return 0;
}
EXPORT_SYMBOL_GPL(crypto_akcipher_sync_prep);
int crypto_akcipher_sync_post(struct crypto_akcipher_sync_data *data, int err)
static int crypto_akcipher_sync_post(struct crypto_akcipher_sync_data *data,
int err)
{
err = crypto_wait_req(err, &data->cwait);
if (data->dst)
memcpy(data->dst, data->buf, data->dlen);
memcpy(data->dst, data->buf, data->dlen);
data->dlen = data->req->dst_len;
kfree_sensitive(data->req);
return err;
}
EXPORT_SYMBOL_GPL(crypto_akcipher_sync_post);
int crypto_akcipher_sync_encrypt(struct crypto_akcipher *tfm,
const void *src, unsigned int slen,
@ -248,34 +251,5 @@ int crypto_akcipher_sync_decrypt(struct crypto_akcipher *tfm,
}
EXPORT_SYMBOL_GPL(crypto_akcipher_sync_decrypt);
static void crypto_exit_akcipher_ops_sig(struct crypto_tfm *tfm)
{
struct crypto_akcipher **ctx = crypto_tfm_ctx(tfm);
crypto_free_akcipher(*ctx);
}
int crypto_init_akcipher_ops_sig(struct crypto_tfm *tfm)
{
struct crypto_akcipher **ctx = crypto_tfm_ctx(tfm);
struct crypto_alg *calg = tfm->__crt_alg;
struct crypto_akcipher *akcipher;
if (!crypto_mod_get(calg))
return -EAGAIN;
akcipher = crypto_create_tfm(calg, &crypto_akcipher_type);
if (IS_ERR(akcipher)) {
crypto_mod_put(calg);
return PTR_ERR(akcipher);
}
*ctx = akcipher;
tfm->exit = crypto_exit_akcipher_ops_sig;
return 0;
}
EXPORT_SYMBOL_GPL(crypto_init_akcipher_ops_sig);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Generic public key cipher type");

View File

@ -22,8 +22,6 @@
#include <linux/sched.h>
#include <linux/types.h>
struct akcipher_request;
struct crypto_akcipher;
struct crypto_instance;
struct crypto_template;
@ -35,19 +33,6 @@ struct crypto_larval {
bool test_started;
};
struct crypto_akcipher_sync_data {
struct crypto_akcipher *tfm;
const void *src;
void *dst;
unsigned int slen;
unsigned int dlen;
struct akcipher_request *req;
struct crypto_wait cwait;
struct scatterlist sg;
u8 *buf;
};
enum {
CRYPTOA_UNSPEC,
CRYPTOA_ALG,
@ -129,10 +114,6 @@ void *crypto_create_tfm_node(struct crypto_alg *alg,
void *crypto_clone_tfm(const struct crypto_type *frontend,
struct crypto_tfm *otfm);
int crypto_akcipher_sync_prep(struct crypto_akcipher_sync_data *data);
int crypto_akcipher_sync_post(struct crypto_akcipher_sync_data *data, int err);
int crypto_init_akcipher_ops_sig(struct crypto_tfm *tfm);
static inline void *crypto_create_tfm(struct crypto_alg *alg,
const struct crypto_type *frontend)
{

View File

@ -5,12 +5,10 @@
* Copyright (c) 2023 Herbert Xu <herbert@gondor.apana.org.au>
*/
#include <crypto/akcipher.h>
#include <crypto/internal/sig.h>
#include <linux/cryptouser.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <linux/seq_file.h>
#include <linux/string.h>
#include <net/netlink.h>
@ -19,8 +17,6 @@
#define CRYPTO_ALG_TYPE_SIG_MASK 0x0000000e
static const struct crypto_type crypto_sig_type;
static void crypto_sig_exit_tfm(struct crypto_tfm *tfm)
{
struct crypto_sig *sig = __crypto_sig_tfm(tfm);
@ -31,9 +27,6 @@ static void crypto_sig_exit_tfm(struct crypto_tfm *tfm)
static int crypto_sig_init_tfm(struct crypto_tfm *tfm)
{
if (tfm->__crt_alg->cra_type != &crypto_sig_type)
return crypto_init_akcipher_ops_sig(tfm);
struct crypto_sig *sig = __crypto_sig_tfm(tfm);
struct sig_alg *alg = crypto_sig_alg(sig);
@ -93,17 +86,9 @@ EXPORT_SYMBOL_GPL(crypto_alloc_sig);
int crypto_sig_maxsize(struct crypto_sig *tfm)
{
if (crypto_sig_tfm(tfm)->__crt_alg->cra_type != &crypto_sig_type)
goto akcipher;
struct sig_alg *alg = crypto_sig_alg(tfm);
return alg->max_size(tfm);
akcipher:
struct crypto_akcipher **ctx = crypto_sig_ctx(tfm);
return crypto_akcipher_maxsize(*ctx);
}
EXPORT_SYMBOL_GPL(crypto_sig_maxsize);
@ -111,26 +96,9 @@ int crypto_sig_sign(struct crypto_sig *tfm,
const void *src, unsigned int slen,
void *dst, unsigned int dlen)
{
if (crypto_sig_tfm(tfm)->__crt_alg->cra_type != &crypto_sig_type)
goto akcipher;
struct sig_alg *alg = crypto_sig_alg(tfm);
return alg->sign(tfm, src, slen, dst, dlen);
akcipher:
struct crypto_akcipher **ctx = crypto_sig_ctx(tfm);
struct crypto_akcipher_sync_data data = {
.tfm = *ctx,
.src = src,
.dst = dst,
.slen = slen,
.dlen = dlen,
};
return crypto_akcipher_sync_prep(&data) ?:
crypto_akcipher_sync_post(&data,
crypto_akcipher_sign(data.req));
}
EXPORT_SYMBOL_GPL(crypto_sig_sign);
@ -138,65 +106,27 @@ int crypto_sig_verify(struct crypto_sig *tfm,
const void *src, unsigned int slen,
const void *digest, unsigned int dlen)
{
if (crypto_sig_tfm(tfm)->__crt_alg->cra_type != &crypto_sig_type)
goto akcipher;
struct sig_alg *alg = crypto_sig_alg(tfm);
return alg->verify(tfm, src, slen, digest, dlen);
akcipher:
struct crypto_akcipher **ctx = crypto_sig_ctx(tfm);
struct crypto_akcipher_sync_data data = {
.tfm = *ctx,
.src = src,
.slen = slen,
.dlen = dlen,
};
int err;
err = crypto_akcipher_sync_prep(&data);
if (err)
return err;
memcpy(data.buf + slen, digest, dlen);
return crypto_akcipher_sync_post(&data,
crypto_akcipher_verify(data.req));
}
EXPORT_SYMBOL_GPL(crypto_sig_verify);
int crypto_sig_set_pubkey(struct crypto_sig *tfm,
const void *key, unsigned int keylen)
{
if (crypto_sig_tfm(tfm)->__crt_alg->cra_type != &crypto_sig_type)
goto akcipher;
struct sig_alg *alg = crypto_sig_alg(tfm);
return alg->set_pub_key(tfm, key, keylen);
akcipher:
struct crypto_akcipher **ctx = crypto_sig_ctx(tfm);
return crypto_akcipher_set_pub_key(*ctx, key, keylen);
}
EXPORT_SYMBOL_GPL(crypto_sig_set_pubkey);
int crypto_sig_set_privkey(struct crypto_sig *tfm,
const void *key, unsigned int keylen)
{
if (crypto_sig_tfm(tfm)->__crt_alg->cra_type != &crypto_sig_type)
goto akcipher;
struct sig_alg *alg = crypto_sig_alg(tfm);
return alg->set_priv_key(tfm, key, keylen);
akcipher:
struct crypto_akcipher **ctx = crypto_sig_ctx(tfm);
return crypto_akcipher_set_priv_key(*ctx, key, keylen);
}
EXPORT_SYMBOL_GPL(crypto_sig_set_privkey);

View File

@ -4131,11 +4131,9 @@ static int test_akcipher_one(struct crypto_akcipher *tfm,
struct crypto_wait wait;
unsigned int out_len_max, out_len = 0;
int err = -ENOMEM;
struct scatterlist src, dst, src_tab[3];
const char *m, *c;
unsigned int m_size, c_size;
const char *op;
u8 *key, *ptr;
struct scatterlist src, dst, src_tab[2];
const char *c;
unsigned int c_size;
if (testmgr_alloc_buf(xbuf))
return err;
@ -4146,92 +4144,53 @@ static int test_akcipher_one(struct crypto_akcipher *tfm,
crypto_init_wait(&wait);
key = kmalloc(vecs->key_len + sizeof(u32) * 2 + vecs->param_len,
GFP_KERNEL);
if (!key)
goto free_req;
memcpy(key, vecs->key, vecs->key_len);
ptr = key + vecs->key_len;
ptr = test_pack_u32(ptr, vecs->algo);
ptr = test_pack_u32(ptr, vecs->param_len);
memcpy(ptr, vecs->params, vecs->param_len);
if (vecs->public_key_vec)
err = crypto_akcipher_set_pub_key(tfm, key, vecs->key_len);
err = crypto_akcipher_set_pub_key(tfm, vecs->key,
vecs->key_len);
else
err = crypto_akcipher_set_priv_key(tfm, key, vecs->key_len);
err = crypto_akcipher_set_priv_key(tfm, vecs->key,
vecs->key_len);
if (err)
goto free_key;
goto free_req;
/*
* First run test which do not require a private key, such as
* encrypt or verify.
*/
/* First run encrypt test which does not require a private key */
err = -ENOMEM;
out_len_max = crypto_akcipher_maxsize(tfm);
outbuf_enc = kzalloc(out_len_max, GFP_KERNEL);
if (!outbuf_enc)
goto free_key;
goto free_req;
if (!vecs->siggen_sigver_test) {
m = vecs->m;
m_size = vecs->m_size;
c = vecs->c;
c_size = vecs->c_size;
op = "encrypt";
} else {
/* Swap args so we could keep plaintext (digest)
* in vecs->m, and cooked signature in vecs->c.
*/
m = vecs->c; /* signature */
m_size = vecs->c_size;
c = vecs->m; /* digest */
c_size = vecs->m_size;
op = "verify";
}
c = vecs->c;
c_size = vecs->c_size;
err = -E2BIG;
if (WARN_ON(m_size > PAGE_SIZE))
if (WARN_ON(vecs->m_size > PAGE_SIZE))
goto free_all;
memcpy(xbuf[0], m, m_size);
memcpy(xbuf[0], vecs->m, vecs->m_size);
sg_init_table(src_tab, 3);
sg_init_table(src_tab, 2);
sg_set_buf(&src_tab[0], xbuf[0], 8);
sg_set_buf(&src_tab[1], xbuf[0] + 8, m_size - 8);
if (vecs->siggen_sigver_test) {
if (WARN_ON(c_size > PAGE_SIZE))
goto free_all;
memcpy(xbuf[1], c, c_size);
sg_set_buf(&src_tab[2], xbuf[1], c_size);
akcipher_request_set_crypt(req, src_tab, NULL, m_size, c_size);
} else {
sg_init_one(&dst, outbuf_enc, out_len_max);
akcipher_request_set_crypt(req, src_tab, &dst, m_size,
out_len_max);
}
sg_set_buf(&src_tab[1], xbuf[0] + 8, vecs->m_size - 8);
sg_init_one(&dst, outbuf_enc, out_len_max);
akcipher_request_set_crypt(req, src_tab, &dst, vecs->m_size,
out_len_max);
akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
crypto_req_done, &wait);
err = crypto_wait_req(vecs->siggen_sigver_test ?
/* Run asymmetric signature verification */
crypto_akcipher_verify(req) :
/* Run asymmetric encrypt */
crypto_akcipher_encrypt(req), &wait);
err = crypto_wait_req(crypto_akcipher_encrypt(req), &wait);
if (err) {
pr_err("alg: akcipher: %s test failed. err %d\n", op, err);
pr_err("alg: akcipher: encrypt test failed. err %d\n", err);
goto free_all;
}
if (!vecs->siggen_sigver_test && c) {
if (c) {
if (req->dst_len != c_size) {
pr_err("alg: akcipher: %s test failed. Invalid output len\n",
op);
pr_err("alg: akcipher: encrypt test failed. Invalid output len\n");
err = -EINVAL;
goto free_all;
}
/* verify that encrypted message is equal to expected */
if (memcmp(c, outbuf_enc, c_size) != 0) {
pr_err("alg: akcipher: %s test failed. Invalid output\n",
op);
pr_err("alg: akcipher: encrypt test failed. Invalid output\n");
hexdump(outbuf_enc, c_size);
err = -EINVAL;
goto free_all;
@ -4239,7 +4198,7 @@ static int test_akcipher_one(struct crypto_akcipher *tfm,
}
/*
* Don't invoke (decrypt or sign) test which require a private key
* Don't invoke decrypt test which requires a private key
* for vectors with only a public key.
*/
if (vecs->public_key_vec) {
@ -4252,13 +4211,12 @@ static int test_akcipher_one(struct crypto_akcipher *tfm,
goto free_all;
}
if (!vecs->siggen_sigver_test && !c) {
if (!c) {
c = outbuf_enc;
c_size = req->dst_len;
}
err = -E2BIG;
op = vecs->siggen_sigver_test ? "sign" : "decrypt";
if (WARN_ON(c_size > PAGE_SIZE))
goto free_all;
memcpy(xbuf[0], c, c_size);
@ -4268,34 +4226,29 @@ static int test_akcipher_one(struct crypto_akcipher *tfm,
crypto_init_wait(&wait);
akcipher_request_set_crypt(req, &src, &dst, c_size, out_len_max);
err = crypto_wait_req(vecs->siggen_sigver_test ?
/* Run asymmetric signature generation */
crypto_akcipher_sign(req) :
/* Run asymmetric decrypt */
crypto_akcipher_decrypt(req), &wait);
err = crypto_wait_req(crypto_akcipher_decrypt(req), &wait);
if (err) {
pr_err("alg: akcipher: %s test failed. err %d\n", op, err);
pr_err("alg: akcipher: decrypt test failed. err %d\n", err);
goto free_all;
}
out_len = req->dst_len;
if (out_len < m_size) {
pr_err("alg: akcipher: %s test failed. Invalid output len %u\n",
op, out_len);
if (out_len < vecs->m_size) {
pr_err("alg: akcipher: decrypt test failed. Invalid output len %u\n",
out_len);
err = -EINVAL;
goto free_all;
}
/* verify that decrypted message is equal to the original msg */
if (memchr_inv(outbuf_dec, 0, out_len - m_size) ||
memcmp(m, outbuf_dec + out_len - m_size, m_size)) {
pr_err("alg: akcipher: %s test failed. Invalid output\n", op);
if (memchr_inv(outbuf_dec, 0, out_len - vecs->m_size) ||
memcmp(vecs->m, outbuf_dec + out_len - vecs->m_size,
vecs->m_size)) {
pr_err("alg: akcipher: decrypt test failed. Invalid output\n");
hexdump(outbuf_dec, out_len);
err = -EINVAL;
}
free_all:
kfree(outbuf_dec);
kfree(outbuf_enc);
free_key:
kfree(key);
free_req:
akcipher_request_free(req);
free_xbuf:

View File

@ -150,16 +150,12 @@ struct drbg_testvec {
struct akcipher_testvec {
const unsigned char *key;
const unsigned char *params;
const unsigned char *m;
const unsigned char *c;
unsigned int key_len;
unsigned int param_len;
unsigned int m_size;
unsigned int c_size;
bool public_key_vec;
bool siggen_sigver_test;
enum OID algo;
};
struct sig_testvec {

View File

@ -12,24 +12,19 @@
#include <linux/crypto.h>
/**
* struct akcipher_request - public key request
* struct akcipher_request - public key cipher request
*
* @base: Common attributes for async crypto requests
* @src: Source data
* For verify op this is signature + digest, in that case
* total size of @src is @src_len + @dst_len.
* @dst: Destination data (Should be NULL for verify op)
* @dst: Destination data
* @src_len: Size of the input buffer
* For verify op it's size of signature part of @src, this part
* is supposed to be operated by cipher.
* @dst_len: Size of @dst buffer (for all ops except verify).
* @dst_len: Size of @dst buffer
* It needs to be at least as big as the expected result
* depending on the operation.
* After operation it will be updated with the actual size of the
* result.
* In case of error where the dst sgl size was insufficient,
* it will be updated to the size required for the operation.
* For verify op this is size of digest part in @src.
* @__ctx: Start of private context data
*/
struct akcipher_request {
@ -55,15 +50,8 @@ struct crypto_akcipher {
};
/**
* struct akcipher_alg - generic public key algorithm
* struct akcipher_alg - generic public key cipher algorithm
*
* @sign: Function performs a sign operation as defined by public key
* algorithm. In case of error, where the dst_len was insufficient,
* the req->dst_len will be updated to the size required for the
* operation
* @verify: Function performs a complete verify operation as defined by
* public key algorithm, returning verification status. Requires
* digest value as input parameter.
* @encrypt: Function performs an encrypt operation as defined by public key
* algorithm. In case of error, where the dst_len was insufficient,
* the req->dst_len will be updated to the size required for the
@ -94,8 +82,6 @@ struct crypto_akcipher {
* @base: Common crypto API algorithm data structure
*/
struct akcipher_alg {
int (*sign)(struct akcipher_request *req);
int (*verify)(struct akcipher_request *req);
int (*encrypt)(struct akcipher_request *req);
int (*decrypt)(struct akcipher_request *req);
int (*set_pub_key)(struct crypto_akcipher *tfm, const void *key,
@ -110,9 +96,9 @@ struct akcipher_alg {
};
/**
* DOC: Generic Public Key API
* DOC: Generic Public Key Cipher API
*
* The Public Key API is used with the algorithms of type
* The Public Key Cipher API is used with the algorithms of type
* CRYPTO_ALG_TYPE_AKCIPHER (listed as type "akcipher" in /proc/crypto)
*/
@ -243,10 +229,9 @@ static inline void akcipher_request_set_callback(struct akcipher_request *req,
*
* @req: public key request
* @src: ptr to input scatter list
* @dst: ptr to output scatter list or NULL for verify op
* @dst: ptr to output scatter list
* @src_len: size of the src input scatter list to be processed
* @dst_len: size of the dst output scatter list or size of signature
* portion in @src for verify op
* @dst_len: size of the dst output scatter list
*/
static inline void akcipher_request_set_crypt(struct akcipher_request *req,
struct scatterlist *src,
@ -347,44 +332,6 @@ int crypto_akcipher_sync_decrypt(struct crypto_akcipher *tfm,
const void *src, unsigned int slen,
void *dst, unsigned int dlen);
/**
* crypto_akcipher_sign() - Invoke public key sign operation
*
* Function invokes the specific public key sign operation for a given
* public key algorithm
*
* @req: asymmetric key request
*
* Return: zero on success; error code in case of error
*/
static inline int crypto_akcipher_sign(struct akcipher_request *req)
{
struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
return crypto_akcipher_alg(tfm)->sign(req);
}
/**
* crypto_akcipher_verify() - Invoke public key signature verification
*
* Function invokes the specific public key signature verification operation
* for a given public key algorithm.
*
* @req: asymmetric key request
*
* Note: req->dst should be NULL, req->src should point to SG of size
* (req->src_size + req->dst_size), containing signature (of req->src_size
* length) with appended digest (of req->dst_size length).
*
* Return: zero on verification success; error code in case of error.
*/
static inline int crypto_akcipher_verify(struct akcipher_request *req)
{
struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
return crypto_akcipher_alg(tfm)->verify(req);
}
/**
* crypto_akcipher_set_pub_key() - Invoke set public key operation
*

View File

@ -124,7 +124,7 @@ static inline struct akcipher_alg *crypto_spawn_akcipher_alg(
/**
* crypto_register_akcipher() -- Register public key algorithm
*
* Function registers an implementation of a public key verify algorithm
* Function registers an implementation of a public key cipher algorithm
*
* @alg: algorithm definition
*
@ -135,7 +135,7 @@ int crypto_register_akcipher(struct akcipher_alg *alg);
/**
* crypto_unregister_akcipher() -- Unregister public key algorithm
*
* Function unregisters an implementation of a public key verify algorithm
* Function unregisters an implementation of a public key cipher algorithm
*
* @alg: algorithm definition
*/