AES_XTS_IVSIZE
memcpy(&blocknum, iv, AES_XTS_IVSIZE);
for (i = 0; i < AES_XTS_IVSIZE; i++) {
bzero(ctx->tweak + AES_XTS_IVSIZE, AES_XTS_IVSIZE);
bcopy(iv, &blocknum, AES_XTS_IVSIZE);
for (i = 0; i < AES_XTS_IVSIZE; i++) {
bzero(ctx->tweak + AES_XTS_IVSIZE, AES_XTS_IVSIZE);