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https://github.com/syncom/tinyp256
A minimum implementation of ECDSA-P256 signature verification with tinycrypt
https://github.com/syncom/tinyp256
curve-p256 ecdsa ecdsa-signature openssl signature-verification
Last synced: 4 days ago
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A minimum implementation of ECDSA-P256 signature verification with tinycrypt
- Host: GitHub
- URL: https://github.com/syncom/tinyp256
- Owner: syncom
- License: mit
- Created: 2023-06-29T04:56:28.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2024-07-01T04:43:21.000Z (5 months ago)
- Last Synced: 2024-07-05T16:07:43.815Z (4 months ago)
- Topics: curve-p256, ecdsa, ecdsa-signature, openssl, signature-verification
- Language: C
- Homepage:
- Size: 39.1 KB
- Stars: 1
- Watchers: 2
- Forks: 2
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# A minimum implementation of ECDSA-P256 signature verification with tinycrypt
This is an implementation of ECDSA signature verification with Curve
[P-256](https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-186.pdf),
based on a minimum subset of source files from the [TinyCrypt cryptographic
library](https://github.com/intel/tinycrypt), with nearly no modification (cf.,
[diffs](./diffs.txt)). It verifies the signature against a 256-bit hash digest
of the payload message: a natural choice of the hash algorithm is SHA-256, and
we will assume it.
The API contains only one function
```c
/**
* @brief Verify an ECDSA-P256 signature on a SHA-256 digest
* @return returns TINYP256_OK if the signature is valid
* returns TINYP256_FAIL if an error occurred or the signature is
* invalid
*
* @param pubkey IN -- ECDSA-P256 public key. Must point to a 64-byte buffer
* containing an uncompressed point in affine coordinates (Qx, Qy)
* @param pubkey_len IN -- Size of public key buffer in bytes. Must be 64.
* @param digest IN -- The SHA-256 digest of the message to verify. Must point to a 32-byte buffer.
* @param digest_len IN -- Size of SHA-256 digest buffer in bytes. Must be 32.
* @param signature IN -- ECDSA-P256 signature value. Must point to a 64-byte buffer
* containing the raw (r, s) value
* @param signature_len IN -- Size of sig buffer in bytes. Must be 64.
*
*/
tinyp256_t tinyp256_verify(
const uint8_t *pubkey, uint16_t pubkey_len,
uint8_t *digest, uint16_t digest_len,
uint8_t *signature, uint16_t signature_len);
```
## Interoperate with OpenSSL
Tested with "OpenSSL 3.1.1 30 May 2023" (Homebrew) on macOS and "OpenSSL 1.1.1
11 Sep 2018" on Ubuntu/Linux.
### Key generation and message signing with OpenSSL
- Generate key pair
Generate private key `private.pem`
```bash
openssl ecparam -name prime256v1 -genkey -noout -out private.pem
```
Get public key `public.pem` from private key
```bash
openssl ec -in private.pem -pubout -out public.pem
```
- Sign payload message, using SHA-256 as message digest
Suppose the payload message to sign is `msg.bin`. Get ECDSA-P256-SHA256
signature `msg.sig.bin`
```bash
openssl dgst -sha256 -sign private.pem -out msg.sig.bin msg.bin
```
Signature can be verified with OpenSSL using command
```bash
# See "Verification OK" upon success, "Verification Failure" otherwise
openssl dgst -verify public.pem -keyform PEM -sha256 \
-signature msg.sig.bin -binary msg.bin
```
Sample files `private.pem`, `public.pem`, `msg.bin` and `msg.sig.bin` can be
found in [testdata/](./testdata/).
### Signature verification with tinyp256
Obtain C-styled bytes arrays pointed to by `pubkey`, `digest` and `signature` as
follows. Feed `tinyp256_verify()` with them for signature verification.
- Public key (`pubkey`)
```bash
openssl ec -pubin -in public.pem -outform DER 2>/dev/null | xxd -i -s 27
```
- SHA-256 hash digest (`digest`) of message to verify
```bash
openssl dgst -sha256 -binary msg.bin | xxd -i
```
- Signature (`signature`)
```bash
openssl asn1parse -in msg.sig.bin -inform DER \
| awk -F':' '{print $4}' \
| awk 'NF > 0' \
| awk '{printf "%064s", $0}' \
| tr ' ' 0 \
| xxd -r -p \
| xxd -i
```
Note that we need to pad the `r`, `s` values in hex with leading zeros so that
they are 32-byte long, if needed - that's what `awk '{printf "%064s", $0} | tr
' ' 0` is for.
Sample byte arrays `pubkey`, `digest` and `signature` can be found in
[test_tinyp256.c](./test_tinyp256.c). To test, in repository's directory root
```bash
make
./test_tinyp256
```