How to use kernel crypto
Hi list,
Recently I'm learning to use kernel crypto. I find some examples but they are out of date.
I manage to write a test program, trying to use aes to encrypt 'buf' ,but something goes wrong:
struct scatterlist sg;
struct crypto_blkcipher *tfm;
struct blkcipher_desc desc;
unsigned char buf[10];
char *key = "00112233445566778899aabbccddeeff";
int keylen = 16;
memset(buf, 'A', 10);
tfm = crypto_alloc_blkcipher("ecb(aes)", 0, CRYPTO_ALG_ASYNC); crypto_blkcipher_setkey(tfm,key,keylen);
desc.tfm = tfm;
desc.flags = 1;sg_init_one(&sg, buf, 10); crypto_blkcipher_encrypt(&desc, &sg, &sg, 10); sg_set_buf(&sg, buf,10);hexdump(buf,10);
The result of hexdump(buf) shows that 'buf' stay unchanged. What should I do to encrypt the buffer?
All the best!
Freeman Zhang
Hi!
Quoted 24 lines · Freeman Zhang
Hi list,
Recently I'm learning to use kernel crypto. I find some examples but they are out of date.
I manage to write a test program, trying to use aes to encrypt 'buf' ,but something goes wrong:struct scatterlist sg;
structcrypto_blkcipher*tfm;
structblkcipher_descdesc;
unsigned char buf[10];
char *key = "00112233445566778899aabbccddeeff";
int keylen = 16;
memset(buf, 'A', 10);
tfm =crypto_alloc_blkcipher("ecb(aes)", 0, CRYPTO_ALG_ASYNC);crypto_blkcipher_setkey(tfm,key,keylen);
desc.tfm = tfm;
desc.flags = 1;sg_init_one(&sg, buf, 10);crypto_blkcipher_encrypt(&desc, &sg, &sg, 10);sg_set_buf(&sg, buf,10);hexdump(buf,10);
Quoted 2 lines
The result of hexdump(buf) shows that 'buf' stay unchanged. What should I do to encrypt the buffer?
Crypto works differently that you probably think it does.
First of all, NEVER NEVER NEVER NEVER NEVER NEVER NEVER use ecb mode. Open wikipedia to see why. This is one of the most basic mistakes you can make.
The reason why the you see plaintext is probably because the buffer size is not a multiple of you aes block size (16 bytes). But I must admit that leaving the data unencrypted instead of e.g. zeroing it does not sound like a good api design to me...
-Michi
Signature · 2 lines
programing a layer 3+4 network protocol for mesh networks see http://michaelblizek.twilightparadox.com
Hi Michi,
Quoted 27 lines · On 14:42 Sun 15 June, michi1 at michaelblizek.twilightparadox.com wrote:
Hi!
Quoted 24 lines · Freeman Zhang
Hi list,
Recently I'm learning to use kernel crypto. I find some examples but they are out of date.
I manage to write a test program, trying to use aes to encrypt 'buf' ,but something goes wrong:struct scatterlist sg;
structcrypto_blkcipher*tfm;
structblkcipher_descdesc;
unsigned char buf[10];
char *key = "00112233445566778899aabbccddeeff";
int keylen = 16;
memset(buf, 'A', 10);
tfm =crypto_alloc_blkcipher("ecb(aes)", 0, CRYPTO_ALG_ASYNC);crypto_blkcipher_setkey(tfm,key,keylen);
desc.tfm = tfm;
desc.flags = 1;sg_init_one(&sg, buf, 10);crypto_blkcipher_encrypt(&desc, &sg, &sg, 10);sg_set_buf(&sg, buf,10);hexdump(buf,10);
Quoted 6 lines
Quoted 2 lines
The result of hexdump(buf) shows that 'buf' stay unchanged. What should I do to encrypt the buffer?
Crypto works differently that you probably think it does.
First of all, NEVER NEVER NEVER NEVER NEVER NEVER NEVER use ecb mode. Open wikipedia to see why. This is one of the most basic mistakes you can make.
No one have told me that. I just pick up one mode randomly. Thanks for the information.
Quoted 2 lines
The reason why the you see plaintext is probably because the buffer size is not a multiple of you aes block size (16 bytes).
Yes, you're right. I'm glad that there is no more plaintext when I simply modified the buffer size to 16.
Quoted 5 lines
But I must admit that leaving
the data unencrypted instead of e.g. zeroing it does not sound like a good api design to me...-Michi
I've checked something about ecb mode and cbc mode. I'm confused by the iv. Is iv only for cbc mode?
How can I set up and initiate iv in the kernel? I don't know where to find an example about this, just try-and-error.
Much thanks !
Freeman
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Hi!
Quoted 3 lines · Freeman Zhang
Hi Michi,
On 14:42 Sun 15 June, michi1 at michaelblizek.twilightparadox.com wrote:
...
Quoted 1 line
iv. Is iv only for cbc mode?
No, it is required for all modes.
Quoted 2 lines
How can I set up and initiate iv in the kernel? I don't know where to find an example about this, just try-and-error.
http://en.wikipedia.org/wiki/Initialization_vector
Setting up the iv is a critical part for your security. You should know what you are doing.
-Michi
Signature · 2 lines
programing a layer 3+4 network protocol for mesh networks see http://michaelblizek.twilightparadox.com