/* * Copyright (c) 2024 Vaughn Nugent * * Package: noscrypt * File: noscrypt.h * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public License * as published by the Free Software Foundation; either version 2.1 * of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public License * along with noscrypt. If not, see http://www.gnu.org/licenses/. */ /* * noscrypt is a an open-source, strict C89 library that performs the basic * cryptographic operations found in the Nostr protocol. It is designed to be * portable and easy to use in any C89 compatible environment. It is also designed */ #pragma once #ifndef NOSCRYPT_H #define NOSCRYPT_H #include #include #include "platform.h" /* Set api export calling convention (allow used to override) */ #ifndef NC_CC #ifdef _NC_IS_WINDOWS /* STD for importing to other languages such as .NET */ #define NC_CC __stdcall #else #define NC_CC #endif #endif /* !NC_CC */ #ifndef NC_EXPORT /* Allow users to disable the export/impoty macro if using source code directly */ #ifdef NOSCRYPT_EXPORTING #ifdef _NC_IS_WINDOWS #define NC_EXPORT __declspec(dllexport) #else #define NC_EXPORT __attribute__((visibility("default"))) #endif /* _NC_IS_WINDOWS */ #else #ifdef _NC_IS_WINDOWS #define NC_EXPORT __declspec(dllimport) #else #define NC_EXPORT #endif /* _NC_IS_WINDOWS */ #endif /* !NOSCRYPT_EXPORTING */ #endif /* !NC_EXPORT */ /* * CONSTANTS */ #define BIP340_PUBKEY_HEADER_BYTE 0x02 #define NIP44_MESSAGE_KEY_SIZE 0x4c /*32 + 12 + 32 = 76 */ #define NC_ENCRYPTION_NONCE_SIZE 0x20 #define NC_SEC_KEY_SIZE 0x20 #define NC_PUBKEY_SIZE 0x20 #define NC_CONTEXT_ENTROPY_SIZE 0x20 #define NC_SHARED_SEC_SIZE 0x20 #define NC_CONV_KEY_SIZE 0x20 #define NC_HMAC_KEY_SIZE 0x20 #define NC_ENCRYPTION_MAC_SIZE 0x20 #define NC_MESSAGE_KEY_SIZE NIP44_MESSAGE_KEY_SIZE /* * From spec * https://github.com/nostr-protocol/nips/blob/master/44.md#decryption */ #define NIP44_MIN_ENC_MESSAGE_SIZE 0x01 #define NIP44_MAX_ENC_MESSAGE_SIZE 0xffff /* * ERROR CODES * * Error codes are 64bit integers. The lower 8 bits are reserved for * the error code, and the upper 8 bits are reserved for the argument * position. * * NCResult type is 64bit to also allow for positive return values for * operations that return a value count. */ #define NC_ARG_POSITION_OFFSET 0x08 #define NC_ERROR_CODE_MASK 0xFF #define NC_SUCCESS 0x00 #define E_NULL_PTR -1 #define E_INVALID_ARG -2 #define E_INVALID_CONTEXT -3 #define E_ARGUMENT_OUT_OF_RANGE -4 #define E_OPERATION_FAILED -5 /* A compressed resul/return value, negative values are failure, 0 is success and positive values are defined by the operation. */ typedef int64_t NCResult; /* An secp256k1 secret key (aka private key buffer) */ typedef struct secret_key_struct { uint8_t key[NC_SEC_KEY_SIZE]; } NCSecretKey; /* An x-only secp256k1 public key */ typedef struct xonly_pubkey_struct { uint8_t key[NC_PUBKEY_SIZE]; } NCPublicKey; /* An opaque full library context object */ typedef struct ctx_struct { void* secpCtx; } NCContext; /* * The encryption arguments structure. This structure is used to pass arguments to the encryption and decryption functions. It stores the data buffers and required nonce used for the stream cipher. */ typedef struct nc_encryption_struct { /* The nonce used for the stream cipher. */ const uint8_t* nonce32; /* The input data buffer to encrypt/decrypt */ const uint8_t* inputData; /* The output data buffer to write data to */ uint8_t* outputData; /* The size of the data buffers. Buffers must * be the same size or larger than this value */ size_t dataSize; } NCEncryptionArgs; /* * A structure for Nip44 message authentication code verification. This structure * is used to pass arguments to the NCVerifyMac and NCVerifyMacEx functions. */ typedef struct nc_mac_verify { /* The message authentication code certifying the Nip44 payload */ const uint8_t* mac32; /* The nonce used for the original message encryption */ const uint8_t* nonce32; /* The message payload data */ const uint8_t* payload; /* The size of the payload data */ size_t payloadSize; } NCMacVerifyArgs; /* API FUNCTIONS */ /* * A helper function to cast a buffer to a NCSecretKey struct * @param key The buffer to cast * @return A pointer to the NCSecretKey struct */ static _nc_fn_inline NCSecretKey* NCToSecKey(uint8_t key[NC_SEC_KEY_SIZE]) { return (NCSecretKey*)key; } /* * A helper function to cast a buffer to a NCPublicKey struct * @param key The buffer to cast * @return A pointer to the NCPublicKey struct */ static _nc_fn_inline NCPublicKey* NCToPubKey(uint8_t key[NC_PUBKEY_SIZE]) { return (NCPublicKey*)key; } static _nc_fn_inline NCResult NCResultWithArgPosition(NCResult err, uint8_t argPosition) { return -(((NCResult)argPosition << NC_ARG_POSITION_OFFSET) | -err); } /* * Parses an error code and returns the error code and the argument position that caused the error. * @param result The error code to parse * @param argPositionOut A pointer to the argument position to write to * @return The error code */ static _nc_fn_inline int NCParseErrorCode(NCResult result, uint8_t* argPositionOut) { /* convert result to a positive value*/ NCResult asPositive; int code; asPositive = -result; /* Get the error code from the lower 8 bits and the argument position from the upper 8 bits*/ code = -(asPositive & NC_ERROR_CODE_MASK); *argPositionOut = (asPositive >> NC_ARG_POSITION_OFFSET) & 0xFF; return code; } /*-------------------------------------- * LIB CONTEXT API */ /* * Runtime check for the size of the context struct to allow for dynamic allocation when context size structure is not known. * @return The size of the context struct in bytes */ NC_EXPORT uint32_t NC_CC NCGetContextStructSize(void); /* * Initializes a context struct with the given entropy * @param ctx A pointer to the context structure to initialize * @param entropy The entropy to initialize the context with * @return NC_SUCCESS if the operation was successful, otherwise an error code */ NC_EXPORT NCResult NC_CC NCInitContext( NCContext* ctx, const uint8_t entropy[NC_CONTEXT_ENTROPY_SIZE] ); /* * Reinitializes a context struct with the given * @param ctx A pointer to the context structure to initialize * @param entropy The entropy to initialize the context with * @return NC_SUCCESS if the operation was successful, otherwise an error code */ NC_EXPORT NCResult NC_CC NCReInitContext( NCContext* ctx, const uint8_t entropy[NC_CONTEXT_ENTROPY_SIZE] ); /* * Destroys a context struct * @param ctx A pointer to the existing context structure to destroy * @return NC_SUCCESS if the operation was successful, otherwise an error code */ NC_EXPORT NCResult NC_CC NCDestroyContext(NCContext* ctx); /*-------------------------------------- * HIGH LEVEL SIGNING API */ /* * Gets a x-only compressed public key from the given secret key * @param ctx A pointer to the existing library context * @param sk A pointer to the secret key * @param pk A pointer to the compressed public key buffer to write to * @return NC_SUCCESS if the operation was successful, otherwise an error code */ NC_EXPORT NCResult NC_CC NCGetPublicKey( const NCContext* ctx, const NCSecretKey* sk, NCPublicKey* pk ); /* * Validates that a given secret key is valid according to the secp256k1 curve. This is functionally the same as calling secp256k1_ec_seckey_verify. * @param ctx A pointer to the existing library context * @param sk A pointer to the secret key to verify * @return 1 if the secret key is valid, 0 if it is not, otherwise an error code */ NC_EXPORT NCResult NC_CC NCValidateSecretKey( const NCContext* ctx, const NCSecretKey* sk ); /* * Signs a raw message after computing the sha256 checksum using the given secret key and writes the signature to the sig64 buffer. * @param ctx A pointer to the existing library context * @param sk A pointer to the secret key to sign with * @param random32 A pointer to the random32 buffer to use for signing * @param data A pointer to the raw data buffer to sign * @param dataSize The size of the raw data buffer * @param sig64 A pointer to the 64byte buffer to write the signature to * @return NC_SUCCESS if the operation was successful, otherwise an error code */ NC_EXPORT NCResult NC_CC NCSignData( const NCContext* ctx, const NCSecretKey* sk, const uint8_t random32[32], const uint8_t* data, const size_t dataSize, uint8_t sig64[64] ); /* * Verifies a signature of a raw data buffer matches the output using the given public key. * @param ctx A pointer to the existing library context * @param sig64 The 64byte signature to verify * @param data A pointer to the raw data buffer to verify * @param dataSize The size of the raw data buffer * @param pk A pointer to the the x-only compressed public key (x-only serialized public key) * @return NC_SUCCESS if the signature could be verified, otherwise an error code */ NC_EXPORT NCResult NC_CC NCVerifyData( const NCContext* ctx, const NCPublicKey* pk, const uint8_t* data, const size_t dataSize, const uint8_t sig64[64] ); /*-------------------------------------- * EXTENDED SIGNING API */ /* * Signs a message using the given secret key and writes the signature to the sig64 buffer * @param ctx A pointer to the existing library context * @param sk A pointer to the secret key to sign with * @param random32 A pointer to the random32 buffer to use for signing * @param digest32 A pointer to sha256 digest32 to sign * @param sig64 A pointer to the 64byte buffer to write the signature to * @return NC_SUCCESS if the operation was successful, otherwise an error code */ NC_EXPORT NCResult NC_CC NCSignDigest( const NCContext* ctx, const NCSecretKey* sk, const uint8_t random32[32], const uint8_t digest32[32], uint8_t sig64[64] ); /* * Verifies a signature of a digest32 matches the output using the given public key. Equivalent to calling secp256k1_schnorrsig_verify. * @param ctx A pointer to the existing library context * @param sig64 The 64byte signature to verify * @param digest32 The digest32 to verify * @param pk A pointer to the the x-only compressed public key (x-only serialized public key) * @return NC_SUCCESS if the signature could be verified, otherwise an error code */ NC_EXPORT NCResult NC_CC NCVerifyDigest( const NCContext* ctx, const NCPublicKey* pk, const uint8_t digest32[32], const uint8_t sig64[64] ); /*-------------------------------------- * HIGH LEVEL ENCRYPTION API */ /* * NOTES * * NIP-44 requires that plaintext/ciphertext must be padded in powers of 2. * Since this library operates on data at the binary level, and does not do * ANY runtime heap allocation, it is up to the user to ensure that the * plaintext/ciphertext buffers are padded properly in The NCryptoData struct * before calling the encryption/decryption functions. */ /* * High level api for encrypting nostr messages using a secret key and a public key. Use the NCEncryptEx functions for extended encryption functionality * @param ctx The library context * @param sk The secret key (the local private key) * @param pk The compressed public key (x-only serialized public key) the other user's public key * @param args The encryption arguments * @param hmacKeyOut A pointer to the buffer to write the hmac key to * @return NC_SUCCESS if the operation was successful, otherwise an error code. Use NCParseErrorCode to the error code and positional argument that caused the error */ NC_EXPORT NCResult NC_CC NCEncrypt( const NCContext* ctx, const NCSecretKey* sk, const NCPublicKey* pk, uint8_t hmacKeyOut[NC_HMAC_KEY_SIZE], NCEncryptionArgs* args ); /* * High level api for decrypting nostr messages using a secret key and a public key. Use the NCDecryptEx functions for extended decryption functionality. * @param ctx The library context * @param sk The secret key (the local private key) * @param pk The compressed public key (x-only serialized public key) the other user's public key * @param args The decryption arguments * @return NC_SUCCESS if the operation was successful, otherwise an error code. Use NCParseErrorCode to the error code and positional argument that caused the error */ NC_EXPORT NCResult NC_CC NCDecrypt( const NCContext* ctx, const NCSecretKey* sk, const NCPublicKey* pk, NCEncryptionArgs* args ); /* * High level api for verifying a Nip44 message authentication code using a secret key and a public key. Use the NCVerifyMacEx functions for extended verification functionality. * @param ctx A pointer to an existing library context * @param sk A pointer to the secret key * @param pk A pointer to the compressed public key (x-only serialized public key) * @param args A pointer to the mac verification arguments * @return NC_SUCCESS if the operation was successful, otherwise an error code. Use NCParseErrorCode to * the error code and positional argument that caused the error */ NC_EXPORT NCResult NC_CC NCVerifyMac( const NCContext* ctx, const NCSecretKey* sk, const NCPublicKey* pk, NCMacVerifyArgs* args ); /*-------------------------------------- * EXTENDED ENCRYPTION API */ /* * Computes a NIP-44 shared secret from a secret key and a public key and stores it in the sharedPoint buffer. * @param ctx A pointer to the existing library context * @param sk The secret key * @param pk The compressed public key (x-only serialized public key) * @param sharedPoint The buffer to store write the secret data to * @return NC_SUCCESS if the operation was successful, otherwise an error code. Use NCParseErrorCode to the error code and positional argument that caused the error */ NC_EXPORT NCResult NC_CC NCGetSharedSecret( const NCContext* ctx, const NCSecretKey* sk, const NCPublicKey* pk, uint8_t sharedPoint[NC_SHARED_SEC_SIZE] ); /* * Computes a NIP-44 conversation key from the local secret key and the remote public key, and stores it in the conversationKey buffer. * @param ctx A pointer to the existing library context * @param sk A pointer to the the secret key * @param pk A pointer to the compressed public key (x-only serialized public key) * @param conversationKey The buffer to store write the conversation key to * @return NC_SUCCESS if the operation was successful, otherwise an error code. Use NCParseErrorCode to the error code and positional argument that caused the error */ NC_EXPORT NCResult NC_CC NCGetConversationKey( const NCContext* ctx, const NCSecretKey* sk, const NCPublicKey* pk, uint8_t conversationKey[NC_CONV_KEY_SIZE] ); /* * Computes a NIP-44 conversation key a shared secret/point, and stores it in the conversationKey buffer. * @param ctx A pointer to the existing library context * @param sharedPoint A pointer to the shared secret/point * @param conversationKey The buffer to store write the conversation key to * @return NC_SUCCESS if the operation was successful, otherwise an error code. Use NCParseErrorCode to the error code and positional argument that caused the error */ NC_EXPORT NCResult NC_CC NCGetConversationKeyEx( const NCContext* ctx, const uint8_t sharedPoint[NC_SHARED_SEC_SIZE], uint8_t conversationKey[NC_CONV_KEY_SIZE] ); /* * Encrypts a message using the given conversation key and writes the encrypted message to the * output buffer. The output buffer must be at least 99 bytes in size. * @param ctx A pointer to the existing library context * @param conversationKey A pointer to the conversation key * @param args A pointer to the encryption arguments structure * @param hmacKeyOut A pointer to the buffer to write the hmac key to * @return NC_SUCCESS if the operation was successful, otherwise an error code. Use NCParseErrorCode to the error code and positional argument that caused the error. */ NC_EXPORT NCResult NC_CC NCEncryptEx( const NCContext* ctx, const uint8_t conversationKey[NC_CONV_KEY_SIZE], uint8_t hmacKeyOut[NC_HMAC_KEY_SIZE], NCEncryptionArgs* args ); /* * Decrypts a message using the given conversation key and writes the decrypted message to the * output buffer. * @param ctx A pointer to the existing library context * @param conversationKey A pointer to the conversation key * @param args A pointer to the decryption arguments structure * @return NC_SUCCESS if the operation was successful, otherwise an error code. Use NCParseErrorCode to the error code and positional argument that caused the error. */ NC_EXPORT NCResult NC_CC NCDecryptEx( const NCContext* ctx, const uint8_t conversationKey[NC_CONV_KEY_SIZE], NCEncryptionArgs* args ); /* * Verifies a Nip44 message authentication code using the given conversation key. * @param ctx A pointer to the existing library context * @param conversationKey A pointer to the conversation key * @param args A pointer to the mac verification arguments * @return NC_SUCCESS if the operation was successful, otherwise an error code. Use NCParseErrorCode to * the error code and positional argument that caused the error. */ NC_EXPORT NCResult NC_CC NCVerifyMacEx( const NCContext* ctx, const uint8_t conversationKey[NC_CONV_KEY_SIZE], NCMacVerifyArgs* args ); /* * Computes a message authentication code for a given payload using the given hmacKey and writes the * mac to the hmacOut buffer. * @param ctx A pointer to the existing library context * @param hmacKey A pointer to the hmac key * @param payload A pointer to the payload data buffer * @param payloadSize The size of the payload data buffer * @param hmacOut A pointer to the buffer to write the mac to * @return NC_SUCCESS if the operation was successful, otherwise an error code. Use NCParseErrorCode to * the error code and positional argument that caused the error. */ NC_EXPORT NCResult NCComputeMac( const NCContext* ctx, const uint8_t hmacKey[NC_HMAC_KEY_SIZE], const uint8_t* payload, size_t payloadSize, uint8_t hmacOut[NC_ENCRYPTION_MAC_SIZE] ); #endif /* !NOSCRYPT_H */