Problem with encrypt and decrypt. Please help

[farizanm84156226]

Here is my code to encrypt and decrypt. When i change my key to decrpt ( 'Mykey1234') i stil can decrypt the string i just encrypted. The key i used to encrypt i 'Mykey12345678'. Any one can explain why this happen?

<cfoutput>
Encrypt : #encrypt('This string will be encrypted (you can replace it with more typing).', 'Mykey12345678', 'CFMX_COMPAT','Base64')#
<cfset new_encrypt = encrypt('This string will be encrypted (you can replace it with more typing).', 'Mykey12345678', 'CFMX_COMPAT','Base64')> <br>
Decrypt : #decrypt(new_encrypt, 'Mykey1234', 'CFMX_COMPAT','Base64')#
</cfoutput>

[farizanm84156226]

Here is my code to encrypt and decrypt. When i change my key to decrpt ( 'Mykey1234') i stil can decrypt the string i just encrypted. The key i used to encrypt i 'Mykey12345678'. Any one can explain why this happen?

<cfoutput>
Encrypt : #encrypt('This string will be encrypted (you can replace it with more typing).', 'Mykey12345678', 'CFMX_COMPAT','Base64')#
<cfset new_encrypt = encrypt('This string will be encrypted (you can replace it with more typing).', 'Mykey12345678', 'CFMX_COMPAT','Base64')> <br>
Decrypt : #decrypt(new_encrypt, 'Mykey1234', 'CFMX_COMPAT','Base64')#
</cfoutput>

[John T Smith]

Please post the exact name of the Adobe program you use so a Moderator may move this message to that forum

[farizanm84156226]

i'm using coldfusion to develope this.

[Manan Joshi]

Moved to Coldfusion forum and also merged the duplicate posts

-Manan

[farizanm84156226]

anybody can help? why i change mykey and i still can decrypt? 

[BKBK]

@farizanm84156226 , what you have discovered is indeed strange. As you can see, I have been able to reproduce the issue with random choices of encryptionKey/decryptionKey pairs.

<cfoutput>
<cfset encryptionKey1="z%KAY012_xyz_abracadabra">
Encrypt1 : #encrypt('This string 1 will be encrypted (you can replace it with more typing).', encryptionKey1, 'CFMX_COMPAT','Base64')#
<cfset new_encrypt1 = encrypt('This string 1 will be encrypted (you can replace it with more typing).', encryptionKey1, 'CFMX_COMPAT','Base64')> <br>

<cfset decryptionKey1="z%KEY012">
Decrypt2 : #decrypt(new_encrypt1, decryptionKey1, 'CFMX_COMPAT','Base64')#<br>
EncryptionKey1 : #encryptionKey1# <br>
DecryptionKey1 : #decryptionKey1# <br><br>

<cfset encryptionKey2="z%key012xxx_xyz_abracadabra">
Encrypt2 : #encrypt('This string 2 will be encrypted (you can replace it with more typing).', encryptionKey2, 'CFMX_COMPAT','Base64')#
<cfset new_encrypt2 = encrypt('This string 2 will be encrypted (you can replace it with more typing).', encryptionKey2, 'CFMX_COMPAT','Base64')> <br>

<cfset decryptionKey2="z%koy012">
Decrypt2 : #decrypt(new_encrypt2, decryptionKey2, 'CFMX_COMPAT','Base64')#<br>
EncryptionKey2 : #encryptionKey2# <br>
DecryptionKey2 : #decryptionKey2# 
</cfoutput>

[BKBK]

On the basis of this finding, my advice is as follows:

• Don't manually generate an encryption key. Instead, use the function generateSecretKey (together with the AES algorithm, for example) to generate the key.
• Store this key, then use it later for decryption.

For example:

<cfoutput>
<cfset encryptionKey=generatesecretkey("AES")>
Encrypt : #encrypt('This string will be encrypted (you can replace it with more typing).', encryptionKey, 'CFMX_COMPAT','Base64')#
<cfset new_encrypt = encrypt('This string will be encrypted (you can replace it with more typing).', encryptionKey, 'CFMX_COMPAT','Base64')> <br>

<cfset decryptionKey=encryptionKey><!--- Stored key used for decryption --->
Decrypt : #decrypt(new_encrypt, decryptionKey, 'CFMX_COMPAT','Base64')#<br>
EncryptionKey : #encryptionKey# <br>
DecryptionKey : #decryptionKey# 
</cfoutput>

[BKBK]

I am on ColdFusion 2021. What is your ColdFusion version and Update level?

[pete_freitag]

CFMX_COMPAT is not really a good choice of algorithm to begin with, if I recall correctly it is just an XOR cipher, so it doesn't provide a lot of assurance. Use something strong like AES instead. 

I never realized that about the key, I imagine it is only using the first few bits of your key, so anything you add to the end of it doesn't matter - this is just another reason to avoid CFMX_COMPAT in my book. 

Pete Freitag

Foundeo Inc.

[John123]

CFMX_COMPAT uses a 32 bit key so the key will always be truncated to the first 8 characters.

[BKBK]

@John123 : CFMX_COMPAT uses a 32 bit key so the key will always be truncated to the first 8 characters.

It's weirder than that I'm afraid. In one of the tests, you could encrypt with the key

z%key012xxx_xyz_abracadabra

and successfully decrypt with

z%koy012

[John123]

@BKBK : another good reason not to use CFMX_COMPAT.

[James Moberg]

FYI: We used these UDFs (from 2005) after the internal cfusion_encrypt & cfusion_decrypt built-in functions were dropped in CF11.
https://www.barneyb.com/barneyblog/2005/10/28/cfusion_encryptcfusion_decrypt-udfs/

<cffunction name="fusion_encrypt" output="false" returntype="string">
	<cfargument name="string" type="string" required="true">
	<cfargument name="key" type="string" required="true">
	<cfset var i = "">
	<cfset var result = "">
	<cfset key = repeatString(key, ceiling(len(string) len(key)))>
	<cfloop from="1" to="#len(string)#" index="i">
	 	 	<cfset result = result & rJustify(formatBaseN(binaryXOR(asc(mid(string, i, 1)), asc(mid(key, i, 1))), 16), 2)>
	</cfloop>
	<cfreturn replace(result, " ", "0", "all")>
</cffunction>
<cffunction name="fusion_decrypt" output="false" returntype="string">
	<cfargument name="string" type="string" required="true">
	<cfargument name="key" type="string" required="true">
	<cfset var i = "">
	<cfset var result = "">
	<cfset key = repeatString(key, ceiling(len(string) 2 len(key)))>
	<cfloop from="2" to="#len(string)#" index="i" step="2">
	 	 	<cfset result = result & chr(binaryXOR(inputBaseN(mid(string, i - 1, 2), 16), asc(mid(key, i 2, 1))))>
	</cfloop>
	<cfreturn result>
</cffunction>
<cffunction name="binaryXOR" output="false" returntype="numeric">
	<cfargument name="n1" type="numeric" required="true">
	<cfargument name="n2" type="numeric" required="true">
	<cfset n1 = formatBaseN(n1, 2)>
	<cfset n2 = formatBaseN(n2, 2)>
	<cfreturn inputBaseN(replace(n1 + n2, 2, 0, "all"), 2)>
</cffunction>

<cfset key = "test">
<cfoutput>
<table>
<cfloop list="barney,is,damn cool!" index="i">
	<tr>
		<td>#i#</td>
		<td>#cfusion_encrypt(i, key)#</td>
		<td>#fusion_encrypt(i, key)#</td>
		<td>#cfusion_decrypt(cfusion_encrypt(i, key), key)#</td>
		<td>#fusion_decrypt(fusion_encrypt(i, key), key)#</td>
	</tr>
</cfloop>
</table>
</cfoutput>

I ran your different encrypt/decrypt keys through it and didn't encounter the same issue (where only the first 8 characters were all that was required to decrypt.)

[BKBK]

@farizanm84156226 , you should report a bug. It might help to include in your report a link to this forum thread.

[BKBK]

Hi @farizanm84156226 , I have reported a bug.

[Brian__]

Bump to an old thread. 🙂  I've added a note to the Bug ID in Tracker too, but this is not a bug. This is how CFMX_COMPAT works (and why it's insecure). The key/seed used for encryption is only 32 bytes (4 characters) and is derived from the user-supplied key.  See https://www.synacktiv.com/en/publications/coldfusion-cfmx_compat-lolcryption.html and https://hoyahaxa.blogspot.com/2023/05/why-you-dont-want-to-use-cfmxcompat.html for more details.

Using a stronger algorithm (such as AES-CBC + validating the integrity of the ciphertext with an HMAC prior to decryption) is a better way to go.