initial addition of essential crypto, encoders, workflows and LLM instructions

pkg/crypto/ec/secp256k1/README.md

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+# secp256k1
+
+> Due to the terrible state of the btcec library, and the ethical character of
+> dcred, the two main secp256k1 EC libraries in the Go language, it has become
+> necessary to refactor and clean up the mess of btcec's module versioning.
+>
+> In addition, the code has been updated to use several new features of Go that
+> were added to the language since these libraries were first created, notably the
+> precomps are here directly generated as binary data instead of nasty base64
+> source code.
+
+Package secp256k1 implements optimized secp256k1 elliptic curve operations.
+
+This package provides an optimized pure Go implementation of elliptic curve
+cryptography operations over the secp256k1 curve as well as data structures and
+functions for working with public and secret secp256k1 keys. See
+https://www.secg.org/sec2-v2.pdf for details on the standard.
+
+In addition, sub packages are provided to produce, verify, parse, and serialize
+ECDSA signatures and EC-Schnorr-DCRv0 (a custom Schnorr-based signature scheme
+specific to Decred) signatures. See the README.md files in the relevant sub
+packages for more details about those aspects.
+
+An overview of the features provided by this package are as follows:
+
+- Secret key generation, serialization, and parsing
+- Public key generation, serialization and parsing per ANSI X9.62-1998
+    - Parses uncompressed, compressed, and hybrid public keys
+    - Serializes uncompressed and compressed public keys
+- Specialized types for performing optimized and constant time field operations
+    - `FieldVal` type for working modulo the secp256k1 field prime
+    - `ModNScalar` type for working modulo the secp256k1 group order
+- Elliptic curve operations in Jacobian projective coordinates
+    - Point addition
+    - Point doubling
+    - Scalar multiplication with an arbitrary point
+    - Scalar multiplication with the base point (group generator)
+- Point decompression from a given x coordinate
+- Nonce generation via RFC6979 with support for extra data and version
+  information that can be used to prevent nonce reuse between signing algorithms
+
+It also provides an implementation of the Go standard library `crypto/elliptic`
+`Curve` interface via the `S256` function so that it may be used with other
+packages in the standard library such as `crypto/tls`, `crypto/x509`, and
+`crypto/ecdsa`. However, in the case of ECDSA, it is highly recommended to use
+the `ecdsa` sub package of this package instead since it is optimized
+specifically for secp256k1 and is significantly faster as a result.
+
+Although this package was primarily written for dcrd, it has intentionally been
+designed so it can be used as a standalone package for any projects needing to
+use optimized secp256k1 elliptic curve cryptography.
+
+Finally, a comprehensive suite of tests is provided to provide a high level of
+quality assurance.