added ecdsa256 doc (#31)

Author: aritkulova

docs/getting-started/Overview.md

@@ -7,7 +7,7 @@
 The library consists of modules and utilities that are built leveraging [Openzeppelin Contracts](https://github.com/OpenZeppelin/openzeppelin-contracts) (4.9.6) and **go far beyond mediocre solidity**.
 
 * Implementation of the [**Contracts Registry**](https://eips.ethereum.org/EIPS/eip-6224) pattern
-* State-of-the-art cryptography primitives (**ECDSA over 384-bit curves**, **RSASSA-PSS**)
+* State-of-the-art cryptography primitives (**ECDSA over 256-bit and 384-bit curves**, **RSASSA-PSS**)
 * Advanced data structures (**Vector**, **DynamicSet**, **PriorityQueue**, **AVLTree**)
 * ZK-friendly [**Sparse Merkle Tree**](https://docs.iden3.io/publications/pdfs/Merkle-Tree.pdf) and [**Incremental Merkle Tree**](https://github.com/runtimeverification/deposit-contract-verification/blob/master/deposit-contract-verification.pdf) implementations
 * Versatile **RBAC** and **MultiOwnable** smart contracts

docs/getting-started/guides/libs/crypto/ecdsa256.md

@@ -0,0 +1,93 @@
+# ╭╯ ECDSA256
+
+## Introduction
+
+This library provides functionality for ECDSA verification over any 256-bit curve.
+
+For more information about the logic behind the contract implementation, please refer to the [OpenZeppelin documentation](https://docs.openzeppelin.com/contracts/5.x/api/utils#P256), particularly the [verifySolidity](https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v5.1.0/contracts/utils/cryptography/P256.sol#L102) function.
+
+## Functions 
+
+To use the `ECDSA256` library, you need to import it.
+
+```solidity
+import "@solarity/solidity-lib/libs/crypto/ECDSA256.sol";
+```
+
+And optionally bind it to the type with the `using` statement.
+
+```solidity
+using ECDSA256 for *;
+```
+
+### verify
+
+```solidity
+function verify(
+    ECDSA256.Parameters memory curveParams_,
+    bytes32 hashedMessage_,
+    bytes memory signature_,
+    bytes memory pubKey_
+) internal view returns (bool)
+```
+
+#### Description
+
+The function to verify the ECDSA signature
+
+##### Parameters:
+
+<table>
+  <thead>
+    <tr>
+      <th>Name</th>
+      <th>Type</th>
+      <th>Description</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td><code>curveParams</code></td>
+      <td>struct ECDSA256.Parameters</td>
+      <td>The 256-bit curve parameters. <code>lowSmax</code> is <code>n/2</code></td>
+    </tr>
+    <tr>
+      <td><code>hashedMessage</code></td>	  
+      <td>bytes32</td>
+      <td>The already hashed message to be verified</td>
+    </tr>
+    <tr>
+      <td><code>signature</code></td>  
+      <td>bytes</td>
+      <td>The ECDSA signature. Equals to <code>bytes(r) + bytes(s)</code></td>
+    </tr>
+    <tr>
+      <td><code>pubKey</code></td>  
+      <td>bytes</td>
+      <td>The full public key of a signer. Equals to <code>bytes(x) + bytes(y)</code>. Note that signatures only from the lower part of the curve are accepted. If your <code>s > n / 2</code>, change it to <code>s = n - s</code></td>
+    </tr>   
+  </tbody>
+</table>
+
+#### Example
+
+```solidity
+function verifySECP256r1(
+    bytes memory message_,
+    bytes memory signature_,
+    bytes memory pubKey_
+) external view returns (bool) {
+	ECDSA256.Parameters memory curveParams_ =
+    ECDSA256.Parameters({
+        a: 0xFFFFFFFF00000001000000000000000000000000FFFFFFFFFFFFFFFFFFFFFFFC,
+        b: 0x5AC635D8AA3A93E7B3EBBD55769886BC651D06B0CC53B0F63BCE3C3E27D2604B,
+        gx: 0x6B17D1F2E12C4247F8BCE6E563A440F277037D812DEB33A0F4A13945D898C296,
+        gy: 0x4FE342E2FE1A7F9B8EE7EB4A7C0F9E162BCE33576B315ECECBB6406837BF51F5,
+        p: 0xFFFFFFFF00000001000000000000000000000000FFFFFFFFFFFFFFFFFFFFFFFF,
+        n: 0xFFFFFFFF00000000FFFFFFFFFFFFFFFFBCE6FAADA7179E84F3B9CAC2FC632551,
+        lowSmax: 0x7fffffff800000007fffffffffffffffde737d56d38bcf4279dce5617e3192a8
+    });
+
+    return curveParams_.verify(sha256(message_), signature_, pubKey_);
+}
+```