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News SpaceX heavy-lift vehicles: Launch Thread

StarCruiser said:
Programs would almost certainly be smaller and would also run faster than they do now. They would probably be more expensive since there would be more code-work to do and you have to pay the programmers (who know what they're doing) for that work.

XCV330 - don't bring up COBOL - unless you mean Kobol:

https://galactica.fandom.com/wiki/Kobol_(TOS)
Click to expand...
TOS-BSG is a holographic universe written in..
8SR7ht1h.jpg
 
I've used Basic (several varieties, some actually not bad), Fortran (several varieties), Algol, Algol 68, Pascal, x86 assembler, 68000 assembler, C, C++, Java, sh, csh, ksh, bash, Matlab, PowerShell, Python, Ruby, Miranda, Lisp, JavaScript, SQL, perl and many others I either can't recall or don't wish to. I don't claim to be anything near expert in any of them. Cobol I never touched. Ada likewise. I'm so old that I was using paper tape and punched cards at one point. I've even used computer consoles with vector rather than raster graphics displays. I used light pens years before I used a mouse.
 
I'm not sure what spacecraft are using nowadays, in the past it was purpose built, IBM based hardware running single task software to keep things as robust as possible.
 
And that's the way anything critical should be... Dedicated to a single task - as bullet proof as you can make it (with an option to reboot when Murphy kicks in)!
 
I have no idea if they still keep it as simple as in the past, if it were my call systems for a spacecraft would have everything in ROM, some RAM and a CPU good enough to run its tasks and thats it, a reboot would just mean that it would reload the needed stuff back to RAM and you can continue to use the machine as if nothing happened.

I assume that they still would build systems like that, a reboot would purge RAM and the system would reload everything the way it was when it was switched on the first time, kinda like the old home computers.
 
I remember watching a movie and can't recall the name but they asked that very question and no one had ever done that on one of their craft due to the expensive nature of them. I just laughed. I mean no one ever thought to test what a reboot would do.
 
Santaman said:
I have no idea if they still keep it as simple as in the past, if it were my call systems for a spacecraft would have everything in ROM, some RAM and a CPU good enough to run its tasks and thats it, a reboot would just mean that it would reload the needed stuff back to RAM and you can continue to use the machine as if nothing happened.

I assume that they still would build systems like that, a reboot would purge RAM and the system would reload everything the way it was when it was switched on the first time, kinda like the old home computers.
Click to expand...
It's kind of useful to be able to change the software in flight though - as on the Voyager spacecraft, where the communications algorithms were updated to handle the increasingly vast distances from Earth and consequent reduced bandwidth and degraded signal-to-noise ratio.
 
StarCruiser said:
Well - to be fair - if all computer programmers had continued to write very tight code, we might still not need more than a few megabytes!
Click to expand...

I wish that had continued. I'm convinced that--somewhere on this planet--is a savant who can think in binary and write a code so tight no one could hack it.

It'd drive him insane and take 20 years to code, but....
 
It's impossible to decrypt ciphertext that is encoded using a one-time pad, provided the pad is not reused and is not available to an adversary. Modern asymmetric key encryption is based on "trap-door" algorithms that are easy to compute in one direction and very difficult to compute in the other direction - an example being the factorisation (very hard) of the product of two primes (very easy).

I'd be interested to know if there is a publicly available encryption technique that can mix two messages with two keys so that each key decrypts only one of the messages. The message would look to all intents and purpose like ciphertext encrypted using a single key, so if the authorities demanded a key, one could hand over the key to a decoy message in the pair. However, perhaps statistical analysis would reveal that the ciphertext contained much more entropy than expected and that another message was probably present.

The most similar method that I can think of was "chaffing and winnowing," which was mooted about 30 years ago by Ron Rivest, but that technique is really neither cryptographic nor steganographic in nature.

ETA: Two messages within a single ciphertext should be possible using two different one-time pads. The authorities would have a hard time proving that the one-time pad that they made you hand over was the wrong one. The number of possible pads is vast and each pad can reproduce a message of equivalent length - although most messages will be garbage, all possible messages of the same length are equally valid.
 
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Asbo Zaprudder said:
ETA: Two messages within a single ciphertext should be possible using two different one-time pads
Click to expand...
One-time pads would be a little bit of a cheat here, so I'm not sure the authorities would buy it. You can claim anything encodes with a one-time pad to anything. For example, you'd get funny (and obviously fake) results if you tried to decode the quoted part of your message with the following one-time pad:
Code: 
CxUSewAkFgZETTcGABIOBB0AFgoABxsdABVPUxoaBgsAABcBFUgoHRsLWBhBHQwGGwtETwxFbREd
BxoIDEwWTxwfSQ8JRFQcBkwIDAJGBB4JTk0AGwYADQMAGQtFAxIBAA==
Here it goes:
Code: 
>>> import binascii
>>> ciphertext = 'ETA: Two messages within a single ciphertext should be possible using two different one-time pads'
>>> onetime_pad = '''
... CxUSewAkFgZETTcGABIOBB0AFgoABxsdABVPUxoaBgsAABcBFUgoHRsLWBhBHQwGGwtETwxFbREd
... BxoIDEwWTxwfSQ8JRFQcBkwIDAJGBB4JTk0AGwYADQMAGQtFAxIBAA==
... '''
>>> key = binascii.a2b_base64(onetime_pad)
>>> cleartext = bytes(map(operator.xor, ciphertext.encode('utf8'), key)).decode('utf8')
>>> print (cleartext)
NASA paid Russian actors to stage the Moon landing on Martian soil and killed all 9 the witnesses
 
publiusr said:
I wish that had continued. I'm convinced that--somewhere on this planet--is a savant who can think in binary and write a code so tight no one could hack it.

It'd drive him insane and take 20 years to code, but....
Click to expand...
Already been done - it's called quantum key distribution. It can be used to set up one-time pads at the two ends of a channel for completely secure communication, which cannot be eavesdropped or spoofed. Companies exist that sell such solutions.
 
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