I thought this is base64 encoding so i try to decode it in that way but it seems this is not base64 encoding. I want to decode this.
O7hrHYO5UUFHFPVILQPc6A==:hEnb3PVrxgHbEL1VT+cu8ic4ocIOfoaWkJ2b2MCrVy4=:jXB0R2OctZ6i1K3s2DlLNS5D/PSdhzKM7GX7gVh6AvXbWrA5i/4j3maFlgk1X2BpmOXYoZab2hAJS4lCBtWi6WnE3zDLhBvWJWFyAN93fIvS66PXJiINmaEhKi8mBIjc
I am learning about reverse eng. and i got this file. This is simple quiz app. (android) in database file it has question with above encoding string. I put here first one. There are many more questions like this.
The colon character : cannot appear in base64 output, and also = can only appear at the end of base64 output, so this string seems to be composed of 3 parts, each individually encoded in base64:
O7hrHYO5UUFHFPVILQPc6A==
hEnb3PVrxgHbEL1VT+cu8ic4ocIOfoaWkJ2b2MCrVy4=
jXB0R2OctZ6i1K3s2DlLNS5D/PSdhzKM7GX7gVh6AvXbWrA5i/4j3maFlgk1X2BpmOXYoZab2hAJS4lCBtWi6WnE3zDLhBvWJWFyAN93fIvS66PXJiINmaEhKi8mBIjc
These don't decode to anything meaningful in base64, so my guess is some encryption scheme has been applied. After decoding, the lengths of these are all multiple of 16 bytes, which hints at a block cipher with blocks of 16 bytes (128 bits).
Related
a question:
A parcel service provider requests that the password is encoded in a specific way:
KEY -> UTF8 Encoding -> SHA512
They KEY should be in byte form, not string
currently I have this in Node.js with CryptoJS:
password = CryptoJS.SHA512(CryptoJS.enc.Utf8.parse(key))
or
password = CryptoJS.SHA512(CryptoJS.enc.Utf8.stringify(key))
Don't know which one is the right one.
I need to convert the key to bytes, how do I do that?
Keys are arbitrary sequences of bytes, and SHA-512 works on arbitrary sequences of bytes. However, UTF-8 can't encode arbitrary sequences of bytes. It can only encode Unicode code points. What you're asking for isn't possible. (I suggest posting precisely what the requirement is. It's possible you're misreading it.)
You need another encoding, such as Base64 or Hex. The output of either of those is compatible with UTF-8 (they both output subsets of UTF-8).
That said, this is a very strange request, since you already have exactly the correct input for SHA-512. Converting it to a string and then converting that string back to (likely different) bytes seems a pointless step, but if you need it, you'll need a byte encoding like Base64 or Hex.
On codejam site they are returning a json string as base64 encoded string.
The actual json payload's size is less than the base64 encoded string.
What's the reason behind returning the payload as base64 encoded string?
7 bit schemes are, or tend to be, transport neutral. There is a natural corruption check as least as good as CRC, and the JSON is less likely to be mangled by well meaning library functions (CRLF, anti-injection, SQL parsing). Yes it's going to be longer. 7 goes into anything more times than 8 (or more).
I understand how to read decimal, binary, hex and base64; that is I can manually convert numbers/counts expressed as each of those bases to expressions in the other bases.
I'm doing the matasano crypto challenges and the very first assignment got me thinking (https://cryptopals.com/sets/1/challenges/1).
The approaches to this problem that I found convert the hexstring to bytes (binary) and then the bytes to base64. Which I understand. Or so I thought. Could I simply concatenate these bytes and say I have the binarystring expression of the same number?
I noticed they basically read the hexstring 2 hexcharacters at a time (because 2 hexcharacters is one byte at most). This results in a binarystring where each binarycharacter(bit) is "aligned" with the hexcharacter(s) it came from.
Does this mean I can just convert this binarystring to decimal and it will be same "number" that the hexstring represents?
Could a similar character-by-character scheme be done to convert to base64? How many hexcharacters per base64character?
#Flimzy shared this link and the way it answered my question is realizing two things:
base16 is an octet based encoding
base64 is a sextet based encoding
I'm in this kind of... Problem... I'm adding to my program the resources by encoding in base64 string the files (images, videos and audio) and adding them to a String. What I do is to read the file and then, convert the bytes to a Base64 string and write it to a txt file, but the txt file occupies slightly MORE space than the original file. Also this happens when I add the string to my program code. The compiled executable occupies a lot of space. Ex:
An MP3 file occupies 2.3 MB
The Base64 string in a txt file occupies 3.19 MB
Any solution or way to optimize the space of base64 string?
P.D. This is just something I'm trying to do for fun. Do not comment below "WHY" or the reason "FOR WHAT" I want this. The answer is: just for fun.
That's inherent to Base64.
Base64 uses 4 octets to encode 3 octets, because it's a reasonably efficient way of encoding arbitrary binary data using just those bytes that mean something printable in ASCII and also avoid many characters that are special in many contexts. It's more compact than say hexadecimal strings (2 octets to encode each octet), but always larger than raw binary. It's value is only in contexts where raw binary won't work, so the extra size is worth it.
(Strictly it's 4 characters to encode 3 octets, so if that was then encoded in UTF-16 or UTF-32 it could be 8 or 16 octets per 3 encoded).
As known, Base-64 encodes binary data into transferable ASCII strings, and we decode these strings back to data.
Now my question is inverted: Can every random string be decoded as binary data, and correctly encoded back to the exact original string?
It depends upon your coding method - some methods use only a limited range of characters so a string containing other characters would not be legal. In Base64 this is the case so the answer is no. With other methods I'm sure its possible but I cannot think of an example other than simply treating the string as binary bytes.