Encrypt and decrypt files using AES encryption technology with the help of the crypto-js library

Question

Encrypt and decrypt files using AES encryption technology with the help of the crypto-js library

I am currently facing a requirement where I am unable to decrypt an encrypted file. Every time I try, the generated file ends up being damaged and cannot be opened. I'm unsure of where the issue lies within my code implementation in VUE.

Encode() {
           let CryptoJS = require("crypto-js");
            this.file_mime = this.file.type;
            this.file_name = this.file.name;
            let reader = new FileReader();
            reader.onload = () => {
                let key = "1234567887654321";
                // let wordArray = CryptoJS.lib.WordArray.create(reader.result);
                // let plaintext = CryptoJS.enc.Hex.stringify(wordArray);
                let encrypted = CryptoJS.AES.encrypt(reader.result, key).toString();

                this.file2 = new Blob([encrypted], {
                    type: this.file_mime
                });
                const a = document.createElement("a");
                const url = window.URL.createObjectURL(this.file2);
                const filename = this.file_name;
                a.href = url;
                a.download = filename;
                a.click();
                window.URL.revokeObjectURL(url);
            };
            reader.readAsBinaryString(this.file);
        }

Decode() {
            let CryptoJS = require("crypto-js");
            let reader = new FileReader();
            reader.onload = () => {
                let key = "1234567887654321";
                let decrypted = CryptoJS.AES.decrypt(reader.result, key).toString(CryptoJS.enc.Utf8)
                this.file2 = new Blob([decrypted], {type: this.file_mime});
                const a = document.createElement("a");
                const url = window.URL.createObjectURL(this.file2);
                const filename = this.file_name;
                a.href = url;
                a.download = filename;
                a.click();
                window.URL.revokeObjectURL(url);
            };
            reader.readAsBinaryString(this.file);
        }

javascript aes cryptojs

Answer 1

Answer №1

When working with JavaScript, it's important to understand the different types of arrays available. These include Array, ArrayBuffer, and typed arrays. Additionally, CryptoJS uses WordArray, requiring proper conversion between these types.

For encryption tasks, it is recommended to replace the usage of FileReader.readAsBinaryString with FileReader.readAsArrayBuffer. This method returns binary data from a file as an ArrayBuffer, which can then be converted to a WordArray for direct processing by CryptoJS.AES.encrypt. The resulting ciphertext is returned as a CipherParams object in Base64 encoded string format following the OpenSSL standard.

During encryption, the key provided to CryptoJS.AES.encrypt is interpreted as a passphrase, generating a random 8-byte salt using the same algorithm employed by OpenSSL to derive the key and initialization vector. The encrypted data starts with specific markers like U2FsdGVkX1 within its Base64 encoding according to the OpenSSL format standards.

Modifications made to the encryption process are outlined below:

function encrypt(input) {
    var file = input.files[0];
    var reader = new FileReader();
    reader.onload = () => {
        var key = "1234567887654321";
        var wordArray = CryptoJS.lib.WordArray.create(reader.result);          
        var encrypted = CryptoJS.AES.encrypt(wordArray, key).toString();        

        var fileEnc = new Blob([encrypted]);                                   
        var a = document.createElement("a");
        var url = window.URL.createObjectURL(fileEnc);
        var filename = file.name + ".enc";
        a.href = url;
        a.download = filename;
        a.click();
        window.URL.revokeObjectURL(url);
    };
    reader.readAsArrayBuffer(file);
}

It is essential to note that encrypted data result in larger file sizes due to the nature of Base64 encoding overhead during encryption compared to unencrypted data.

Similarly, for decryption operations, replacing FileReader.readAsBinaryString with FileReader.readAsText enables passing the Base64 encoded data directly to CryptoJS.AES.decrypt. The decrypted content is returned as a WordArray, necessitating further conversion steps to create the final output blob.

function decrypt(input) {
    var file = input.files[0];
    var reader = new FileReader();
    reader.onload = () => {
        var key = "1234567887654321";  

        var decrypted = CryptoJS.AES.decrypt(reader.result, key);               
        var typedArray = convertWordArrayToUint8Array(decrypted);               

        var fileDec = new Blob([typedArray]);                                   

        var a = document.createElement("a");
        var url = window.URL.createObjectURL(fileDec);
        var filename = file.name.substr(0, file.name.length - 4) + ".dec";
        a.href = url;
        a.download = filename;
        a.click();
        window.URL.revokeObjectURL(url);
    };
    reader.readAsText(file);
}

Answer 2

When working with JavaScript, it's important to understand the different types of arrays available. These include Array, ArrayBuffer, and typed arrays. Additionally, CryptoJS uses WordArray, requiring proper conversion between these types.

For encryption tasks, it is recommended to replace the usage of FileReader.readAsBinaryString with FileReader.readAsArrayBuffer. This method returns binary data from a file as an ArrayBuffer, which can then be converted to a WordArray for direct processing by CryptoJS.AES.encrypt. The resulting ciphertext is returned as a CipherParams object in Base64 encoded string format following the OpenSSL standard.

During encryption, the key provided to CryptoJS.AES.encrypt is interpreted as a passphrase, generating a random 8-byte salt using the same algorithm employed by OpenSSL to derive the key and initialization vector. The encrypted data starts with specific markers like U2FsdGVkX1 within its Base64 encoding according to the OpenSSL format standards.

Modifications made to the encryption process are outlined below:

function encrypt(input) {
    var file = input.files[0];
    var reader = new FileReader();
    reader.onload = () => {
        var key = "1234567887654321";
        var wordArray = CryptoJS.lib.WordArray.create(reader.result);          
        var encrypted = CryptoJS.AES.encrypt(wordArray, key).toString();        

        var fileEnc = new Blob([encrypted]);                                   
        var a = document.createElement("a");
        var url = window.URL.createObjectURL(fileEnc);
        var filename = file.name + ".enc";
        a.href = url;
        a.download = filename;
        a.click();
        window.URL.revokeObjectURL(url);
    };
    reader.readAsArrayBuffer(file);
}

It is essential to note that encrypted data result in larger file sizes due to the nature of Base64 encoding overhead during encryption compared to unencrypted data.

Similarly, for decryption operations, replacing FileReader.readAsBinaryString with FileReader.readAsText enables passing the Base64 encoded data directly to CryptoJS.AES.decrypt. The decrypted content is returned as a WordArray, necessitating further conversion steps to create the final output blob.

function decrypt(input) {
    var file = input.files[0];
    var reader = new FileReader();
    reader.onload = () => {
        var key = "1234567887654321";  

        var decrypted = CryptoJS.AES.decrypt(reader.result, key);               
        var typedArray = convertWordArrayToUint8Array(decrypted);               

        var fileDec = new Blob([typedArray]);                                   

        var a = document.createElement("a");
        var url = window.URL.createObjectURL(fileDec);
        var filename = file.name.substr(0, file.name.length - 4) + ".dec";
        a.href = url;
        a.download = filename;
        a.click();
        window.URL.revokeObjectURL(url);
    };
    reader.readAsText(file);
}

Encrypt and decrypt files using AES encryption technology with the help of the crypto-js library

Answer №1

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