crypto stuff

1 files changed, 80 insertions, 0 deletions

diff --git a/client-web/source/protocol/crypto.ts b/client-web/source/protocol/crypto.ts
new file mode 100644
index 0000000..6cd2ba3
--- /dev/null
+++ b/client-web/source/protocol/crypto.ts
@@ -0,0 +1,80 @@
+import { log } from "../logger.ts";
+
+//! I am not a crypto expert at all! Please read carefully and report any issues to me. 
+
+export async function crypto_seeded_key(seed: string): Promise<CryptoKey> {
+    log("crypto", "importing seed…")
+    const seed_key = await window.crypto.subtle.importKey(
+        "raw",
+        new TextEncoder().encode(seed),
+        "PBKDF2",
+        false,
+        ["deriveKey"]
+    )
+    //? TODO is it possible to use a unique seed per session here? 
+    // const salt = window.crypto.getRandomValues(new Uint8Array(16));
+    const salt = base64_to_buf("thisisagoodsaltAAAAAAA==") // valid "unique" 16-byte base-64 string
+    log("crypto", "deriving key…")
+    const key = await window.crypto.subtle.deriveKey(
+        {
+            name: "PBKDF2",
+            salt,
+            iterations: 250000,
+            hash: "SHA-256",
+        },
+        seed_key,
+        { name: "AES-GCM", length: 256 },
+        false,
+        ["encrypt", "decrypt"]
+    )
+    console.log(key);
+    log("crypto", "ready")
+    return key
+}
+
+export async function crypto_encrypt(key: CryptoKey, data: string): Promise<string> {
+    const iv = window.crypto.getRandomValues(new Uint8Array(12));
+    const ciphertext = new Uint8Array(await window.crypto.subtle.encrypt(
+        { name: "AES-GCM", iv },
+        key,
+        new TextEncoder().encode(data)
+    ));
+    const buf = new Uint8Array(iv.byteLength + ciphertext.byteLength);
+    buf.set(iv, 0);
+    buf.set(ciphertext, iv.byteLength);
+    const b64 = buf_to_base64(buf);
+    return b64;
+}
+
+export async function crypt_decrypt(key: CryptoKey, data: string): Promise<string> {
+    const buf = base64_to_buf(data);
+    const iv = buf.slice(0, 12);
+    const ciphertext = buf.slice(12);
+    const decryptedContent = await window.crypto.subtle.decrypt(
+        { name: "AES-GCM", iv },
+        key,
+        ciphertext
+    );
+    const plain = new TextDecoder().decode(decryptedContent);
+    return plain
+}
+
+// const buf_to_base64 = (buf: Uint8Array) => btoa(String.fromCharCode.apply(null, buf));
+// const base64_to_buf = (b64: string) => Uint8Array.from(atob(b64), (c) => c.charCodeAt(0));
+
+export function base64_to_buf(data: string): Uint8Array {
+    const binary_string = globalThis.atob(data);
+    const bytes = new Uint8Array(binary_string.length);
+    for (let i = 0; i < binary_string.length; i++) {
+        bytes[i] = binary_string.charCodeAt(i);
+    }
+    return bytes;
+}
+
+export function buf_to_base64(bytes: Uint8Array): string {
+    let binary = '';
+    for (let i = 0; i < bytes.byteLength; i++) {
+        binary += String.fromCharCode(bytes[i]);
+    }
+    return globalThis.btoa(binary);
+}
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