Supra_App/src/lib/core/utils/crypto.ts

export class WebCryptoHelper {
	static async generateKeyPair() {
		const keyPair = await window.crypto.subtle.generateKey(
			{
				name: 'ECDH',
				namedCurve: 'P-256'
			},
			true,
			['deriveKey', 'deriveBits']
		);

		const exportedPublic = await window.crypto.subtle.exportKey('raw', keyPair.publicKey);
		const publicKeyBase64 = btoa(String.fromCharCode(...new Uint8Array(exportedPublic)));

		return { privateKey: keyPair.privateKey, publicKeyBase64 };
	}

	static async deriveSharedKey(clientPrivateKey: any, serverPublicKeyBase64: any) {
		const binarySign = atob(serverPublicKeyBase64);
		const bytes = new Uint8Array(binarySign.length);
		for (let i = 0; i < binarySign.length; i++) {
			bytes[i] = binarySign.charCodeAt(i);
		}

		const importedServerPublic = await window.crypto.subtle.importKey(
			'raw',
			bytes,
			{ name: 'ECDH', namedCurve: 'P-256' },
			true,
			[]
		);
		return await window.crypto.subtle.deriveKey(
			{ name: 'ECDH', public: importedServerPublic },
			clientPrivateKey,
			{ name: 'AES-GCM', length: 256 },
			true,
			['encrypt', 'decrypt']
		);
	}

	static async decryptMessage(aesKey: any, ciphertextBase64: any, ivBase64: any) {
		const rawCipher = Uint8Array.from(atob(ciphertextBase64), (c) => c.charCodeAt(0));
		const rawIv = Uint8Array.from(atob(ivBase64), (c) => c.charCodeAt(0));
		const decryptedBuffer = await window.crypto.subtle.decrypt(
			{ name: 'AES-GCM', iv: rawIv },
			aesKey,
			rawCipher
		);
		return new TextDecoder().decode(decryptedBuffer);
	}

	// Encrypt outgoing messages before sending them to your Axum backend
	static async encryptMessage(aesKey: any, plainText: any) {
		const iv = window.crypto.getRandomValues(new Uint8Array(12)); // 12-byte nonce
		const encodedText = new TextEncoder().encode(plainText);

		const ciphertextBuffer = await window.crypto.subtle.encrypt(
			{ name: 'AES-GCM', iv: iv },
			aesKey,
			encodedText
		);

		const ciphertextBase64 = btoa(String.fromCharCode(...new Uint8Array(ciphertextBuffer)));
		const ivBase64 = btoa(String.fromCharCode(...iv));

		return { ciphertext: ciphertextBase64, iv: ivBase64 };
	}
}