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Add examples to EVP_EncryptInit manual page.

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This commit is contained in:
Dr. Stephen Henson 2001-05-17 13:03:20 +00:00
parent b49a5b2dc0
commit 181355616e
1 changed files with 89 additions and 0 deletions
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89
doc/crypto/EVP_EncryptInit.pod
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@ -367,6 +367,95 @@ Set the effective key length used in RC2:
int key_bits;
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_SET_RC2_KEY_BITS, key_bits, NULL);
Encrypt a string using blowfish:
int do_crypt(char *outfile)
{
unsigned char outbuf[1024];
int outlen, tmplen;
/* Bogus key and IV: we'd normally set these from
* another source.
*/
unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
unsigned char iv[] = {1,2,3,4,5,6,7,8};
char intext[] = "Some Crypto Text";
EVP_CIPHER_CTX ctx;
FILE *out;
EVP_EncryptInit(&ctx, EVP_bf_cbc(), key, iv);
if(!EVP_EncryptUpdate(&ctx, outbuf, &outlen, intext, strlen(intext)))
{
/* Error */
return 0;
}
/* Buffer passed to EVP_EncryptFinal() must be after data just
* encrypted to avoid overwriting it.
*/
if(!EVP_EncryptFinal(&ctx, outbuf + outlen, &tmplen))
{
/* Error */
return 0;
}
outlen += tmplen;
EVP_CIPHER_CTX_cleanup(&ctx);
/* Need binary mode for fopen because encrypted data is
* binary data. Also cannot use strlen() on it because
* it wont be null terminated and may contain embedded
* nulls.
*/
out = fopen(outfile, "wb");
fwrite(outbuf, 1, outlen, out);
fclose(out);
return 1;
}
The ciphertext from the above example can be decrypted using the B<openssl>
utility with the command line:
S<openssl bf -in cipher.bin -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708 -d>
General encryption, decryption function example using FILE I/O and RC2 with an
80 bit key:
int do_crypt(FILE *in, FILE *out, int do_encrypt)
{
/* Allow enough space in output buffer for additional block */
inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
int inlen, outlen;
/* Bogus key and IV: we'd normally set these from
* another source.
*/
unsigned char key[] = "0123456789";
unsigned char iv[] = "12345678";
/* Don't set key or IV because we will modify the parameters */
EVP_CipherInit(&ctx, EVP_rc2(), NULL, NULL, do_encrypt);
EVP_CIPHER_CTX_set_key_length(&ctx, 10);
/* We finished modifying parameters so now we can set key and IV */
EVP_CipherInit(&ctx, NULL, key, iv, do_encrypt);
for(;;)
{
inlen = fread(inbuf, 1, 1024, in);
if(inlen <= 0) break;
if(!EVP_CipherUpdate(&ctx, outbuf, &outlen, inbuf, inlen))
{
/* Error */
return 0;
}
fwrite(outbuf, 1, outlen, out);
}
if(!EVP_CipherFinal(&ctx, outbuf, &outlen))
{
/* Error */
return 0;
}
fwrite(outbuf, 1, outlen, out);
EVP_CIPHER_CTX_cleanup(&ctx);
return 1;
}
=head1 SEE ALSO
L<evp(3)|evp(3)>