man shishi_decrypt_ivupdate (3): API function

SYNOPSIS

#include <shishi.h>

int shishi_decrypt_ivupdate(Shishi * handle, Shishi_key * key, int keyusage, const char * iv, size_t ivlen, char ** ivout, size_t * ivoutlen, const char * in, size_t inlen, char ** out, size_t * outlen);

ARGUMENTS

Shishi * handle: shishi handle as allocated by shishi_init().
Shishi_key * key: key to decrypt with.
int keyusage: integer specifying what this key is decrypting.
const char * iv: input array with initialization vector
size_t ivlen: size of input array with initialization vector.
char ** ivout: output array with newly allocated updated initialization vector.
size_t * ivoutlen: size of output array with updated initialization vector.
const char * in: input array with data to decrypt.
size_t inlen: size of input array with data to decrypt.
char ** out: output array with newly allocated decrypted data.
size_t * outlen: output variable with size of newly allocated output array.

DESCRIPTION

Decrypts data using specified initialization vector and key. The key actually used is derived using the key usage. If key usage is 0, no key derivation is used. The OUT buffer must be deallocated by the caller. If IVOUT or IVOUTLEN is NULL, the updated IV is not saved anywhere.

Note that DECRYPT(ENCRYPT(data)) does not necessarily yield data exactly. Some encryption types add pad to make the data fit into the block size of the encryption algorithm. Furthermore, the pad is not guaranteed to look in any special way, although existing implementations often pad with the zero byte. This means that you may have to "frame" data, so it is possible to infer the original length after decryption. Compare ASN.1 DER which contains such information.

RETURN VALUE

Returns SHISHI_OK iff successful.

REPORTING BUGS

Report bugs to <[email protected]>.

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