diff --git a/static/resources/NibblePoker/libs/crc32.mjs b/static/resources/NibblePoker/libs/crc32.mjs
new file mode 100644
index 0000000..f941156
--- /dev/null
+++ b/static/resources/NibblePoker/libs/crc32.mjs
@@ -0,0 +1,33 @@
+
+/**
+ * @param data {Uint8Array}
+ * @param crc32 {number}
+ * @return {number}
+ */
+export function stepCrc32IEEE(data, crc32 = 0xffffffff) {
+	for (let i = 0; i < data.length; i++) {
+		crc32 ^= data[i];
+		for (let j = 0; j < 8; j++) {
+			crc32 = (crc32 >>> 1) ^ (crc32 & 1 ? 0xedb88320 : 0);
+		}
+	}
+	return crc32;
+}
+
+/**
+ * @param crc32 {number}
+ * @return {number}
+ */
+export function finishCrc32IEEE(crc32) {
+	return (crc32 ^ 0xffffffff) >>> 0;
+}
+
+/**
+ * Calculates the CRC32-IEEE for the given data
+ * @param data {Uint8Array}
+ * @param crc32 {number}
+ * @return {number} The resulting CRC32
+ */
+export function crc32IEEE(data, crc32 = 0xffffffff) {
+	return finishCrc32IEEE(stepCrc32IEEE(data, crc32));
+}
diff --git a/static/resources/NibblePoker/libs/data-utils.mjs b/static/resources/NibblePoker/libs/data-utils.mjs
index aafca04..71859cf 100644
--- a/static/resources/NibblePoker/libs/data-utils.mjs
+++ b/static/resources/NibblePoker/libs/data-utils.mjs
@@ -50,3 +50,36 @@ export function peekUInt32LE(data, offset = 0) {
     }
     return new DataView(data.buffer, offset, 4).getUint32(0, true);
 }
+
+/**
+ * Converts a given `Uint8Array` to a hexadecimal representation.
+ * @param data The data to be transformed into a string.
+ * @return {string} The resulting hexadecimal string.
+ */
+export function Uint8ArrayToHex(data) {
+    return Array.prototype.map.call(data, x => ('00' + x.toString(16)).slice(-2)).join('');
+}
+
+/*export function decimalToHexString(number) {
+	if (number < 0) {
+		number = 0xFFFFFFFF + number + 1;
+	}
+	return number.toString(16).toUpperCase();
+}*/
+
+export function AsciiStringToUint8Array(asciiText) {
+    return Uint8Array.from(Array.from(asciiText).map(asciiLetter => asciiLetter.charCodeAt(0)));
+}
+
+export function Int32ToUint8Array(number) {
+    /*let arr = new ArrayBuffer(4);
+    new DataView(arr).setUint32(0, number);
+    return new Uint8Array(arr);*/
+
+    return new Uint8Array([
+        (number >>> 24) & 0xFF,
+        (number >>> 16) & 0xFF,
+        (number >>> 8) & 0xFF,
+        number & 0xFF
+    ]);
+}
diff --git a/static/resources/NibblePoker/libs/png-utils.mjs b/static/resources/NibblePoker/libs/png-utils.mjs
index 7485557..dfb38f3 100644
--- a/static/resources/NibblePoker/libs/png-utils.mjs
+++ b/static/resources/NibblePoker/libs/png-utils.mjs
@@ -1,6 +1,6 @@
 
-//import {__crc32, crc32b, _crc32b, decimalToHexString} from "./crc32.mjs";
-import {areUintArraysEqual, peekUInt32BE, peekUInt32LE} from "./data-utils.mjs"
+import {stepCrc32IEEE, finishCrc32IEEE} from "./crc32.mjs";
+import {areUintArraysEqual, peekUInt32BE, AsciiStringToUint8Array, Int32ToUint8Array, Uint8ArrayToHex} from "./data-utils.mjs"
 import {loadFileAsUint8Array} from "./file-utils.mjs";
 
 /**
@@ -14,8 +14,12 @@ export class PngInvalidStructureError extends PngError {}
 
 export class PngInvalidChunkNameError extends PngError {}
 
+export class PngInvalidChunkChecksumError extends PngError {}
+
 export class PngInvalidImageHeaderError extends PngError {}
 
+export class PngMissingCriticalChunksError extends PngError {}
+
 export const PngFileHeader = new Uint8Array([0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A]);
 
 export class PngChunk {
@@ -34,10 +38,29 @@ export class PngChunk {
     constructor(type, data, expectedChecksum) {
         this.type = type;
         this.data = data;
+
+        if(expectedChecksum !== null) {
+            if(!areUintArraysEqual(expectedChecksum, this.getChecksumUint8Array())) {
+                throw new PngInvalidChunkChecksumError(
+                    `Invalid checksum was given ! (Expected ${
+                        Uint8ArrayToHex(expectedChecksum)}, got ${
+                        Uint8ArrayToHex(this.getChecksumUint8Array())})`
+                );
+            }
+        }
     }
 
-    getChecksum() {
-        throw new Error("This function isn't implemented yet !");
+    getChecksumNumber() {
+        return finishCrc32IEEE(
+            stepCrc32IEEE(
+                this.data,
+                stepCrc32IEEE(AsciiStringToUint8Array(this.type))
+            )
+        )
+    }
+
+    getChecksumUint8Array() {
+        return Int32ToUint8Array(this.getChecksumNumber());
     }
 }
 
@@ -111,17 +134,22 @@ export class PngFile {
     /**
      * @param file {File|null}
      * @param fileData {Uint8Array|null}
-     * @throws PngInvalidFileHeaderError If the `fileData` is provided and doesn't contain a valid PNG file header.
+     * @throws PngInvalidFileHeaderError If `fileData` is provided and doesn't contain a valid PNG file header.
+     * @throws PngMissingCriticalChunksError If `fileData` is provided and is missing some critical chunks.
      */
     constructor(file = null, fileData = null) {
         this.originalFile = file;
 
         this.chunks = [];
 
-        // Parsing the data
+        // Parsing and validating the data if given
         if(fileData !== null) {
             this.#validateFileHeader(fileData);
             this.#parseChunks(fileData);
+
+            if(!this.hasEndChunk() || this.getChunkByType("IHDR") === null) {
+                throw new PngMissingCriticalChunksError("One or more critical chunk is missing from the PNG file !");
+            }
         }
     }