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Default Random Bit Generator

I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)

Thanks!

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
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Default Random Bit Generator

In article ,
Jim Thompson writes:
I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)


Do you want real random or just pseudo random?

If pseudo random is good enough, google for LFSR. With the right
polynomial, you get a random sequence of (2^N)-1 bits. There are
tables of polynomials that do that. Some of them need only 1 XOR
gate.

--
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Default Random Bit Generator

On Wed, 20 Oct 2010 14:34:38 -0700, Jim Thompson
wrote:

I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)


---
Whoopeee!!!

Right up my alley!

Do you want truly random or pseudorandom, and if pseudorandom how long
do you want the output to be before it repeats?


---
JF
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Default Random Bit Generator

On Wed, 20 Oct 2010 17:23:54 -0500, John Fields
wrote:

On Wed, 20 Oct 2010 14:34:38 -0700, Jim Thompson
wrote:

I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)


---
Whoopeee!!!

Right up my alley!

Do you want truly random or pseudorandom, and if pseudorandom how long
do you want the output to be before it repeats?


---
JF


Pseudo-random is just fine. I just need it to test an
encoding/decoding chip design. A hundred bits or so before repeat
would be quite adequate. No security involved... just testing to be
sure of no decoding hiccups.

Thanks!

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I can see November from my house :-)
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Default Random Bit Generator


I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)


How random do you need it to be?

If you want truly or statistically-close-to-really random, it's a Hard
Problem. You'd probably want something like an avalanche or other
noise diode, amplified, and then fed into a comparator... shield and
filter the bleep out of it to keep it from being pulled around by
external noise. Latch the output of the comparator on each clock
pulse and you've got reasonably random bits.

If you're willing to accept pseudo-random bits (chaotic-looking, but
actually predictable), a cheap and easy solution is a maximal-length
linear feedback shift register. These require a shift register of
suitable width (feel free to daisy-chain several 74HC595 or similar)
and an N-input XOR. You simply XOR several of the parallel outputs of
the shift register together and feed this back into the shift-register
inputs. If you pick these tapped outputs correctly (creating a
primitive polynomial mod 2), the output bitstream will have a period
of 2^N-1 before it repeats (where N is the width of the shift register).

You have to be careful to pre-load the register with at least one "1"
bit at reset time... it'll stick at zero, otherwise.

Schneier's "Applied Cryptography" has a table of suitable primitive
polynomials on pages 376-377. Some of them are rather huge... if you
want a 3217-bit shift register version, he's got two of them!

There are several which would be pretty easy to implement, and have a
good long repeat period... 60 to 64 bits, with at most 5 inputs to the
XOR.

For more sophisticated LFSRs, you can:

- Run several of them of different lengths (each with its own feedback
chain), and XOR the results.

- Use an "alternating stop and go" generator, which uses three LFSRs
of different lengths and feedback taps. One generator "A" is
shifted on every clock; its output controls which of the other two
"B" and "C" is shifted during that clock; the final output is
taken by XORing the output bits of "B" and "C". This architecture
has the effect of "hiding" the raw outputs of the LFSRs from
visibility, and makes determining the LFSR feedback coefficients
quite a bit harder.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!


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Default Random Bit Generator



Jim Thompson wrote:

On Wed, 20 Oct 2010 17:23:54 -0500, John Fields
wrote:


On Wed, 20 Oct 2010 14:34:38 -0700, Jim Thompson
wrote:


I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)


---
Whoopeee!!!

Right up my alley!

Do you want truly random or pseudorandom, and if pseudorandom how long
do you want the output to be before it repeats?


---
JF



OT:

Question: Why it is impossible to have sex in the middle of the Red
Square in Moscow?

Answer: Because every idiot bystander will be eager to give his
invaluable advice.

Here is my invaluable advice: make a ring of the odd number of
invertors, compute a logical function from this ring.


Pseudo-random is just fine. I just need it to test an
encoding/decoding chip design. A hundred bits or so before repeat
would be quite adequate. No security involved... just testing to be
sure of no decoding hiccups.


Take a binary counter, compute some ugly logical function from its output.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
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Default Random Bit Generator

On Wed, 20 Oct 2010 18:04:19 -0500, Vladimir Vassilevsky
wrote:



Jim Thompson wrote:

On Wed, 20 Oct 2010 17:23:54 -0500, John Fields
wrote:


On Wed, 20 Oct 2010 14:34:38 -0700, Jim Thompson
wrote:


I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)

---
Whoopeee!!!

Right up my alley!

Do you want truly random or pseudorandom, and if pseudorandom how long
do you want the output to be before it repeats?


---
JF



OT:

Question: Why it is impossible to have sex in the middle of the Red
Square in Moscow?

Answer: Because every idiot bystander will be eager to give his
invaluable advice.

Here is my invaluable advice: make a ring of the odd number of
invertors, compute a logical function from this ring.


Pseudo-random is just fine. I just need it to test an
encoding/decoding chip design. A hundred bits or so before repeat
would be quite adequate. No security involved... just testing to be
sure of no decoding hiccups.


Take a binary counter, compute some ugly logical function from its output.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com


Vladimir, What's your definition of "ugly" ?:-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I can see November from my house :-)
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Default Random Bit Generator

"Jim Thompson" schreef
in bericht ...
I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)

Thanks!

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.


Ever saved the schematic below. FAIK it's from John Fields.

petrus bitbyter

Version 4
SHEET 1 1140 680
WIRE 1008 -496 -320 -496
WIRE -384 -480 -432 -480
WIRE -432 -448 -432 -480
WIRE -432 -448 -480 -448
WIRE 464 -432 -320 -432
WIRE -544 -400 -880 -400
WIRE -432 -384 -480 -384
WIRE 224 -368 -320 -368
WIRE -432 -352 -432 -384
WIRE -384 -352 -432 -352
WIRE -256 -304 -320 -304
WIRE 704 -224 96 -224
WIRE -880 -192 -880 -400
WIRE -880 -192 -928 -192
WIRE 464 -192 464 -432
WIRE 464 -192 96 -192
WIRE 32 -176 -784 -176
WIRE -16 -160 -784 -160
WIRE 224 -160 224 -368
WIRE 224 -160 96 -160
WIRE -992 -144 -1056 -144
WIRE -256 -144 -256 -304
WIRE -256 -144 -784 -144
WIRE -848 -128 -928 -128
WIRE -496 -128 -784 -128
WIRE -736 -112 -784 -112
WIRE 944 64 -1216 64
WIRE -864 112 -1136 112
WIRE -624 112 -864 112
WIRE -384 112 -624 112
WIRE -144 112 -384 112
WIRE 96 112 -144 112
WIRE 336 112 96 112
WIRE 576 112 336 112
WIRE 816 112 576 112
WIRE -864 160 -864 112
WIRE -624 160 -624 112
WIRE -384 160 -384 112
WIRE -144 160 -144 112
WIRE 96 160 96 112
WIRE 336 160 336 112
WIRE 576 160 576 112
WIRE 816 160 816 112
WIRE -1056 208 -1056 -144
WIRE -944 208 -1056 208
WIRE -736 208 -736 -112
WIRE -736 208 -784 208
WIRE -704 208 -736 208
WIRE -496 208 -496 -128
WIRE -496 208 -544 208
WIRE -464 208 -496 208
WIRE -256 208 -256 -144
WIRE -256 208 -304 208
WIRE -224 208 -256 208
WIRE -16 208 -16 -160
WIRE -16 208 -64 208
WIRE 16 208 -16 208
WIRE 224 208 224 -160
WIRE 224 208 176 208
WIRE 256 208 224 208
WIRE 464 208 464 -192
WIRE 464 208 416 208
WIRE 496 208 464 208
WIRE 704 208 704 -224
WIRE 704 208 656 208
WIRE 736 208 704 208
WIRE 1008 208 1008 -496
WIRE 1008 208 896 208
WIRE -976 256 -1056 256
WIRE -944 256 -976 256
WIRE -704 256 -736 256
WIRE -464 256 -496 256
WIRE -224 256 -256 256
WIRE 16 256 -16 256
WIRE 256 256 224 256
WIRE 496 256 464 256
WIRE 736 256 704 256
WIRE -1216 288 -1216 64
WIRE -1056 288 -1056 256
WIRE -976 352 -976 256
WIRE -736 352 -736 256
WIRE -736 352 -976 352
WIRE -496 352 -496 256
WIRE -496 352 -736 352
WIRE -256 352 -256 256
WIRE -256 352 -496 352
WIRE -16 352 -16 256
WIRE -16 352 -256 352
WIRE 224 352 224 256
WIRE 224 352 -16 352
WIRE 464 352 464 256
WIRE 464 352 224 352
WIRE 704 352 704 256
WIRE 704 352 464 352
WIRE -1216 384 -1216 368
WIRE -1136 384 -1136 112
WIRE -1136 384 -1216 384
WIRE -1056 384 -1056 368
WIRE -1056 384 -1136 384
WIRE -864 384 -864 304
WIRE -624 384 -624 304
WIRE -624 384 -864 384
WIRE -384 384 -384 304
WIRE -384 384 -624 384
WIRE -144 384 -144 304
WIRE -144 384 -384 384
WIRE 96 384 96 304
WIRE 96 384 -144 384
WIRE 336 384 336 304
WIRE 336 384 96 384
WIRE 576 384 576 304
WIRE 576 384 336 384
WIRE 816 384 816 304
WIRE 816 384 576 384
WIRE 944 384 944 64
WIRE 944 384 816 384
WIRE -1216 432 -1216 384
FLAG -1216 432 0
SYMBOL voltage -1056 272 R0
WINDOW 3 24 104 Invisible 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR Value PULSE(0 5 0 1e-6 1e-6 .001 .002)
SYMATTR InstName V1
SYMBOL Digital\\dflop -864 160 R0
SYMATTR InstName A5
SYMATTR SpiceLine Td=10n tripdt=10n trise=30n vhigh=5
SYMBOL Digital\\xor -976 -96 R180
WINDOW 3 16 112 Invisible 0
SYMATTR Value trise 10e-9 vhigh 5v
SYMATTR InstName A14
SYMBOL Digital\\dflop -624 160 R0
SYMATTR InstName A1
SYMATTR SpiceLine Td=10n tripdt=10n trise=30n vhigh=5
SYMBOL Digital\\dflop -384 160 R0
SYMATTR InstName A2
SYMATTR SpiceLine Td=10n tripdt=10n trise=30n vhigh=5
SYMBOL Digital\\dflop -144 160 R0
SYMATTR InstName A3
SYMATTR SpiceLine Td=10n tripdt=10n trise=30n vhigh=5
SYMBOL Digital\\dflop 96 160 R0
SYMATTR InstName A6
SYMATTR SpiceLine Td=10n tripdt=10n trise=30n vhigh=5
SYMBOL Digital\\dflop 336 160 R0
SYMATTR InstName A7
SYMATTR SpiceLine Td=10n tripdt=10n trise=30n vhigh=5
SYMBOL Digital\\dflop 576 160 R0
SYMATTR InstName A8
SYMATTR SpiceLine Td=10n tripdt=10n trise=30n vhigh=5
SYMBOL Digital\\dflop 816 160 R0
SYMATTR InstName A9
SYMATTR SpiceLine Td=10n tripdt=10n trise=30n vhigh=5
SYMBOL Digital\\xor -528 -352 R180
WINDOW 3 16 112 Invisible 0
SYMATTR Value trise 10e-9 vhigh 5v
SYMATTR InstName A4
SYMBOL Digital\\xor -368 -528 M0
WINDOW 3 16 112 Invisible 0
SYMATTR Value trise 10e-9 vhigh 5v
SYMATTR InstName A10
SYMBOL Digital\\xor -368 -400 M0
WINDOW 3 16 112 Invisible 0
SYMATTR Value trise 10e-9 vhigh 5v
SYMATTR InstName A11
SYMBOL Digital\\or 64 -128 R180
WINDOW 3 -8 128 Invisible 0
SYMATTR Value trise 10e-9 vhigh 5v
SYMATTR InstName A12
SYMBOL Digital\\or -816 -208 M0
WINDOW 3 -8 128 Invisible 0
SYMATTR Value trise 10e-9 vhigh 5v
SYMATTR InstName A13
SYMBOL voltage -1216 272 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 3 24 104 Invisible 0
SYMATTR InstName V2
SYMATTR Value PULSE(5 0 1e-6)
TEXT -1192 408 Left 0 !.tran 0 .512 0



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Default Random Bit Generator

On Wed, 20 Oct 2010 18:04:19 -0500, Vladimir Vassilevsky
wrote:



Jim Thompson wrote:

On Wed, 20 Oct 2010 17:23:54 -0500, John Fields
wrote:


On Wed, 20 Oct 2010 14:34:38 -0700, Jim Thompson
wrote:


I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)

---
Whoopeee!!!

Right up my alley!

Do you want truly random or pseudorandom, and if pseudorandom how long
do you want the output to be before it repeats?


---
JF



OT:

Question: Why it is impossible to have sex in the middle of the Red
Square in Moscow?

Answer: Because every idiot bystander will be eager to give his
invaluable advice.


---
You, included?
---

Here is my invaluable advice: make a ring of the odd number of
invertors, compute a logical function from this ring.


Pseudo-random is just fine. I just need it to test an
encoding/decoding chip design. A hundred bits or so before repeat
would be quite adequate. No security involved... just testing to be
sure of no decoding hiccups.


Take a binary counter, compute some ugly logical function from its output.


---
Ouch!

I'm sadly disappointed, since from your earlier posts I thought that
you were more sophisticated than you now seem to be.

---
JF
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Default Random Bit Generator


Xilinx XAPP052 - Efficient Shift Registers, LFSR Counters, and Long
Pseudo-Random Sequence Generators. Gives tables for LFSR generators
from 3 to 168 bits in length.


In article , Jim Thompson
wrote:

I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)

Thanks!

...Jim Thompson


--


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Default Random Bit Generator

On Wed, 20 Oct 2010 18:03:32 -0700, artie
wrote:


Xilinx XAPP052 - Efficient Shift Registers, LFSR Counters, and Long
Pseudo-Random Sequence Generators. Gives tables for LFSR generators
from 3 to 168 bits in length.


In article , Jim Thompson
wrote:

I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)

Thanks!

...Jim Thompson


74HCxxxx ??

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I can see November from my house :-)
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Default Random Bit Generator

Jim Thompson wrote:

I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)


I'd like to see somebody hack into one of those radioactive smoke detectors,
and use the radioactive decay, maybe XOR it into a PSRG.

Cheers!
Rich

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Default Random Bit Generator

Vladimir Vassilevsky wrote:

Question: Why it is impossible to have sex in the middle of the Red
Square in Moscow?

Answer: Because every idiot bystander will be eager to give his
invaluable advice.

Here is my invaluable advice: make a ring of the odd number of
invertors, compute a logical function from this ring.

If you're going hiking alone, be sure to bring along a deck of cards.

That way, if you get lost, you can sit down, start to play solitaire,
and someone will show up to help. ;-)

Cheers!
Rich

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Default Random Bit Generator

Xilinx XAPP052 - Efficient Shift Registers, LFSR Counters, and Long
Pseudo-Random Sequence Generators. Gives tables for LFSR generators
from 3 to 168 bits in length.


74HCxxxx ??


It's just FFs and an XOR gate.
It's pretty easy to translate to 74HC.


--
These are my opinions, not necessarily my employer's. I hate spam.

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Default Random Bit Generator


Take a binary counter, compute some ugly logical function from its output.


The problem is that "ugly" functions have a long history of being
not as random as you would like.

You could use a ROM and some software to generate the contents.
But I don't know any 74HC parts that are ROMs.

LFSR is best solution to Jim's problem that I know of.

--
These are my opinions, not necessarily my employer's. I hate spam.



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Default Random Bit Generator

On Wed, 20 Oct 2010 15:45:35 -0700, Jim Thompson
wrote:

On Wed, 20 Oct 2010 17:23:54 -0500, John Fields
wrote:

On Wed, 20 Oct 2010 14:34:38 -0700, Jim Thompson
wrote:

I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)


---
Whoopeee!!!

Right up my alley!

Do you want truly random or pseudorandom, and if pseudorandom how long
do you want the output to be before it repeats?


---
JF


Pseudo-random is just fine. I just need it to test an
encoding/decoding chip design. A hundred bits or so before repeat
would be quite adequate. No security involved... just testing to be
sure of no decoding hiccups.


Try a 74hc164 and a 74hc7266. Connect QF and QG to A input through one
of the gates in the 7266. Apply clear and clock to 164. You should get
a 127 bit PRBS.
--
Muzaffer Kal

DSPIA INC.
ASIC/FPGA Design Services

http://www.dspia.com
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Default Random Bit Generator

On Wed, 20 Oct 2010 22:41:22 -0700, Muzaffer Kal
wrote:

On Wed, 20 Oct 2010 15:45:35 -0700, Jim Thompson
wrote:

On Wed, 20 Oct 2010 17:23:54 -0500, John Fields
wrote:

On Wed, 20 Oct 2010 14:34:38 -0700, Jim Thompson
wrote:

I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)

---
Whoopeee!!!

Right up my alley!

Do you want truly random or pseudorandom, and if pseudorandom how long
do you want the output to be before it repeats?


---
JF


Pseudo-random is just fine. I just need it to test an
encoding/decoding chip design. A hundred bits or so before repeat
would be quite adequate. No security involved... just testing to be
sure of no decoding hiccups.


Try a 74hc164 and a 74hc7266. Connect QF and QG to A input through one
of the gates in the 7266. Apply clear and clock to 164. You should get
a 127 bit PRBS.


Thanks! That's pretty much what I had decided... except all the
LFSR/PRBS pages are all confusing as hell to an Analog guy :-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I can see November from my house :-)
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Default Random Bit Generator

On Thu, 21 Oct 2010 10:10:56 -0700, Jim Thompson
wrote:

On Thu, 21 Oct 2010 08:13:45 -0500, John Fields
wrote:

Unlabeled gate below....

My 'HC164 has A, B as inputs, which I assumed were your D1, D2 inputs
until I noticed the unlabeled device.


---
Sorry about that, it's one of the gates in an HC86.

---
JF
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Default Random Bit Generator

On Thu, 21 Oct 2010 12:59:08 -0500, John Fields
wrote:

On Thu, 21 Oct 2010 10:10:56 -0700, Jim Thompson
wrote:

On Thu, 21 Oct 2010 08:13:45 -0500, John Fields
wrote:

Unlabeled gate below....

My 'HC164 has A, B as inputs, which I assumed were your D1, D2 inputs
until I noticed the unlabeled device.


---
Sorry about that, it's one of the gates in an HC86.

---
JF


OK. Thanks!

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I can see November from my house :-)
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Default Random Bit Generator

On 21/10/2010 7:34 AM, Jim Thompson wrote:
I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)

Thanks!

...Jim Thompson



I posted some pages of Applied Cryptography he

http://www.filedropper.com/lfsr

The pages contain the information you need to build dozens of different
LFSR's of maximum period using a couple of 74... series. IIRC you can
replace the XOR function with NXOR and get a maximal period LSFR that
will self start (the all zero startup state becomes a valid state for
the LSFR)


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Default Random Bit Generator

On Fri, 22 Oct 2010 07:54:13 +1000, David Eather
wrote:

On 21/10/2010 7:34 AM, Jim Thompson wrote:
I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)

Thanks!

...Jim Thompson



I posted some pages of Applied Cryptography he

http://www.filedropper.com/lfsr

The pages contain the information you need to build dozens of different
LFSR's of maximum period using a couple of 74... series. IIRC you can
replace the XOR function with NXOR and get a maximal period LSFR that
will self start (the all zero startup state becomes a valid state for
the LSFR)


Link times out :-(

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
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I can see November from my house :-)
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Default Random Bit Generator

On Fri, 22 Oct 2010 07:54:13 +1000, David Eather
wrote:

On 21/10/2010 7:34 AM, Jim Thompson wrote:
I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)

Thanks!

...Jim Thompson



I posted some pages of Applied Cryptography he

http://www.filedropper.com/lfsr

The pages contain the information you need to build dozens of different
LFSR's of maximum period using a couple of 74... series. IIRC you can
replace the XOR function with NXOR and get a maximal period LSFR that
will self start (the all zero startup state becomes a valid state for
the LSFR)


Link times out :-(

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I can see November from my house :-)
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Default Random Bit Generator

On 22/10/2010 8:23 AM, Jim Thompson wrote:
On Fri, 22 Oct 2010 07:54:13 +1000, David
wrote:

On 21/10/2010 7:34 AM, Jim Thompson wrote:
I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)

Thanks!

...Jim Thompson



I posted some pages of Applied Cryptography he

http://www.filedropper.com/lfsr

The pages contain the information you need to build dozens of different
LFSR's of maximum period using a couple of 74... series. IIRC you can
replace the XOR function with NXOR and get a maximal period LSFR that
will self start (the all zero startup state becomes a valid state for
the LSFR)


Link times out :-(

...Jim Thompson


Send PM - I'll PM the zip file (0.5 Mb)
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Default Random Bit Generator

I'm only getting 52 before a repeat :-(
(I'm looking at the serial stream.)


Get rid of that reset kludgery.

LFSRs with the right taps will cycle through 2^N-1 states.
The other state is stable.

The stable state is all 0s or all 1s. You can switch to the other one
with an inverter.


--
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Default Random Bit Generator


Thanks! That's pretty much what I had decided... except all the
LFSR/PRBS pages are all confusing as hell to an Analog guy :-)


It will click when you see it. The key idea is Finite State Machine.
With N flip-flops, the best you can do is 2^N states. A counter
gets them all, but it's not random.

A LFSR with the right taps gets 2^N-1, and they happen to be a
"nice" random pattern. They are widely used in gear for testing
communication links.



Horowitz and Hill, Art of Electronics, has a nice section starting
on page 655. It's only 3 pages, no hairy math.

The Wikipedia article on LFSRs is good:
http://en.wikipedia.org/wiki/Linear_...shift_register

--
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Default Random Bit Generator


Thanks! That's pretty much what I had decided... except all the
LFSR/PRBS pages are all confusing as hell to an Analog guy :-)


It will click when you see it. The key idea is Finite State Machine.
With N flip-flops, the best you can do is 2^N states. A counter
gets them all, but it's not random.

A LFSR with the right taps gets 2^N-1, and they happen to be a
"nice" random pattern. They are widely used in gear for testing
communication links.



Horowitz and Hill, Art of Electronics, has a nice section starting
on page 655. It's only 3 pages, no hairy math.

The Wikipedia article on LFSRs is good:
http://en.wikipedia.org/wiki/Linear_...shift_register

--
These are my opinions, not necessarily my employer's. I hate spam.

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Default Random Bit Generator

On Fri, 22 Oct 2010 08:25:17 +1000, David Eather
wrote:

On 22/10/2010 8:23 AM, Jim Thompson wrote:
On Fri, 22 Oct 2010 07:54:13 +1000, David
wrote:

On 21/10/2010 7:34 AM, Jim Thompson wrote:
I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)

Thanks!

...Jim Thompson


I posted some pages of Applied Cryptography he

http://www.filedropper.com/lfsr

The pages contain the information you need to build dozens of different
LFSR's of maximum period using a couple of 74... series. IIRC you can
replace the XOR function with NXOR and get a maximal period LSFR that
will self start (the all zero startup state becomes a valid state for
the LSFR)


Link times out :-(

...Jim Thompson


Send PM - I'll PM the zip file (0.5 Mb)


OK. Got it working. Repeats at 255.

What was confusing me was the double-talk about numbering the
shift-register stages. Must be Physics majors who still have their
direction of current reversed ;-)

Thanks again, David!

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I can see November from my house :-)
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Default Random Bit Generator

On Fri, 22 Oct 2010 08:25:17 +1000, David Eather
wrote:

On 22/10/2010 8:23 AM, Jim Thompson wrote:
On Fri, 22 Oct 2010 07:54:13 +1000, David
wrote:

On 21/10/2010 7:34 AM, Jim Thompson wrote:
I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)

Thanks!

...Jim Thompson


I posted some pages of Applied Cryptography he

http://www.filedropper.com/lfsr

The pages contain the information you need to build dozens of different
LFSR's of maximum period using a couple of 74... series. IIRC you can
replace the XOR function with NXOR and get a maximal period LSFR that
will self start (the all zero startup state becomes a valid state for
the LSFR)


Link times out :-(

...Jim Thompson


Send PM - I'll PM the zip file (0.5 Mb)


OK. Got it working. Repeats at 255.

What was confusing me was the double-talk about numbering the
shift-register stages. Must be Physics majors who still have their
direction of current reversed ;-)

Thanks again, David!

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I can see November from my house :-)
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Default Random Bit Generator

Jim Thompson wrote:
On Fri, 22 Oct 2010 08:25:17 +1000, David Eather
On 22/10/2010 8:23 AM, Jim Thompson wrote:
On Fri, 22 Oct 2010 07:54:13 +1000, David

http://www.filedropper.com/lfsr

The pages contain the information you need to build dozens of different
LFSR's of maximum period using a couple of 74... series. IIRC you can
replace the XOR function with NXOR and get a maximal period LSFR that
will self start (the all zero startup state becomes a valid state for
the LSFR)

Link times out :-(


Send PM - I'll PM the zip file (0.5 Mb)


OK. Got it working. Repeats at 255.

What was confusing me was the double-talk about numbering the
shift-register stages. Must be Physics majors who still have their
direction of current reversed ;-)

Nah - it's a digital nerd thing - Typically, for a binary output, Q0,
Q1, ... Qn, the bit position corresponds to that power of two. As far as
which way you shift, there's a holy war between little-endian and
big-endian, but ssentially, it's a coin toss. :-)

Cheers!
Rich

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John Fields wrote:
On Thu, 21 Oct 2010 15:01:42 -0700, Jim Thompson
On Thu, 21 Oct 2010 08:13:45 -0500, John Fields
On Wed, 20 Oct 2010 15:45:35 -0700, Jim Thompson
On Wed, 20 Oct 2010 17:23:54 -0500, John Fields
On Wed, 20 Oct 2010 14:34:38 -0700, Jim Thompson

I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)

Whoopeee!!!

Right up my alley!

Do you want truly random or pseudorandom, and if pseudorandom how long
do you want the output to be before it repeats?

Pseudo-random is just fine. I just need it to test an
encoding/decoding chip design. A hundred bits or so before repeat
would be quite adequate. No security involved... just testing to be
sure of no decoding hiccups.


[ASCIImatic snipped]

The diodes and the inverter make a 7 input NOR which keeps the thing
from latching up, ever, and gives you all 256 states from 00 to ff.


I'm only getting 52 before a repeat :-(

(I'm looking at the serial stream.)


Strange.

Those taps are supposed to yield a maximal length sequence (2^n-1),
and the pulse-stuffer is supposed to force the sequence to include the
lockup state, yielding 2^n states between repeats.

I'll get on it tomorrow and, hopefully, find where the problem lies.

In the meantime, I apologize for the inconvenience.

Do I dare mention Don Lancaster's TTL Cookbook? He's got schematics up to
some fairly long length - I don't recall off the top of my head how long,
but it's definitely more than 16.

Cheers!
Rich



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Default Random Bit Generator

Hal Murray wrote:

I'm only getting 52 before a repeat :-(
(I'm looking at the serial stream.)


Get rid of that reset kludgery.

LFSRs with the right taps will cycle through 2^N-1 states.
The other state is stable.

The stable state is all 0s or all 1s. You can switch to the other one
with an inverter.

That's there in case some random glitch inserts or removes a bit,
accidentally leading to the stuck state.

Cheers!
Rich


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Default Random Bit Generator


Jim Thompson wrote:

I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)



XOR some of Sloman's messages. ;-)


--
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enough left over to pay them.
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Default Random Bit Generator

On Thu, 21 Oct 2010 15:01:42 -0700, Jim Thompson
wrote:


I'm only getting 52 before a repeat :-(

(I'm looking at the serial stream.)

...Jim Thompson


Aaargh!

Sorry about that...

Normally the counter jumps over the all-zeroes lockup state and runs
at a length of 2^n - 1.

The error here (egg on face) was that by forcing the counter into the
all-zeroes state, once every cycle, a lot (all?) of the states which
would have existed on the other side of the jump are killed off.

The right way, if starting up in (or accidentally falling into) the
all zeroes state is a concern, is to NOR all the Q's and feed the NOR
output to the XOR, as shown.

That way, the counter runs at maximal length normally, but forces a 1
into the shift register's serial input if its outputs all go to 0, for
whatever reason.

---
JF
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Jim Thompson wrote:

I'd like to conjure up a random bit generator.


Question: Why it is impossible to have sex in the middle of the Red
Square in Moscow?

Answer: Because every idiot bystander will be eager to give his
invaluable advice.


So everybody is suggesting the LSFR. LSFRs are trivial; zero state
problem has to be dealt with. I try doing something different just for
the sake ot it.

Take a binary counter, compute some ugly logical function from its output.

Vladimir, What's your definition of "ugly" ?:-)


Take two binary counters. One counts to 2^N, the other one counts to
some odd number. Compute parity function of both counters. Here you go.

Take a binary adder and a register. Add some odd number at every cycle.
Tale a bit somewhere from the middle of the register.

Take a binary adder and a register. Multiply by (2^N - 1), i.e.
leftshift and subtract. Set the LSB to 1 to avoid all zero state.

There is approximately a zillion of ways of making quazi random (or true
random) generator from whatever stuff you got in the drawers. BTW, some
25 years ago I made random generator from relays. However, that was LSFR :-)



Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
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Vladimir Vassilevsky wrote:


Jim Thompson wrote:

I'd like to conjure up a random bit generator.


Question: Why it is impossible to have sex in the middle of the Red
Square in Moscow?

Answer: Because every idiot bystander will be eager to give his
invaluable advice.


So everybody is suggesting the LSFR. LSFRs are trivial; zero state
problem has to be dealt with. I try doing something different just for
the sake ot it.

Take a binary counter, compute some ugly logical function from its
output.

Vladimir, What's your definition of "ugly" ?:-)


Take two binary counters. One counts to 2^N, the other one counts to
some odd number. Compute parity function of both counters. Here you go.

Take a binary adder and a register. Add some odd number at every cycle.
Tale a bit somewhere from the middle of the register.

Take a binary adder and a register. Multiply by (2^N - 1), i.e.
leftshift and subtract. Set the LSB to 1 to avoid all zero state.

There is approximately a zillion of ways of making quazi random (or true
random) generator from whatever stuff you got in the drawers. BTW, some
25 years ago I made random generator from relays. However, that was LSFR
:-)



Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

One CANNOT compute (or generate from logic) a truly random number.
Now, quasi-random number generators are a dime a dozen, like you imply.


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On Fri, 22 Oct 2010 00:53:55 -0400, "Michael A. Terrell"
wrote:


Jim Thompson wrote:

I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)



XOR some of Sloman's messages. ;-)


Those aren't very random. He keeps saying the same stuff, over and
over.

John

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John Larkin wrote:

On Fri, 22 Oct 2010 00:53:55 -0400, "Michael A. Terrell"
wrote:


Jim Thompson wrote:

I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)



XOR some of Sloman's messages. ;-)


Those aren't very random. He keeps saying the same stuff, over and
over.



If you XOR enough of them, the typos add up into a random mess.

--
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enough left over to pay them.
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Default Random Bit Generator



Robert Baer wrote:
Vladimir Vassilevsky wrote:


There is approximately a zillion of ways of making quazi random (or
true random) generator from whatever stuff you got in the drawers.


One CANNOT compute (or generate from logic) a truly random number.


Sure you can. Just make a long enough daisy chain of logic gates and
compute a logic function from the input and the output of the chain. Now
apply a clock to the input. As pulse propagates through the chain, the
RMS jitter will add up and the output of the function will be truly
random. Ring Oscillators are the other example, but they are asynchronous.

Now, quasi-random number generators are a dime a dozen, like you imply.


Oh, I forgot to mention the whole class of PRNGs where one counter acts
as a source of the clock for the other counter. That is simple and
allows generation of the variety of random looking sequencies.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
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On Sat, 23 Oct 2010 20:00:32 -0700, Robert Baer
wrote:

Vladimir Vassilevsky wrote:


Jim Thompson wrote:

I'd like to conjure up a random bit generator.


Question: Why it is impossible to have sex in the middle of the Red
Square in Moscow?

Answer: Because every idiot bystander will be eager to give his
invaluable advice.


So everybody is suggesting the LSFR. LSFRs are trivial; zero state
problem has to be dealt with. I try doing something different just for
the sake ot it.

Take a binary counter, compute some ugly logical function from its
output.

Vladimir, What's your definition of "ugly" ?:-)


Take two binary counters. One counts to 2^N, the other one counts to
some odd number. Compute parity function of both counters. Here you go.

Take a binary adder and a register. Add some odd number at every cycle.
Tale a bit somewhere from the middle of the register.

Take a binary adder and a register. Multiply by (2^N - 1), i.e.
leftshift and subtract. Set the LSB to 1 to avoid all zero state.

There is approximately a zillion of ways of making quazi random (or true
random) generator from whatever stuff you got in the drawers. BTW, some
25 years ago I made random generator from relays. However, that was LSFR
:-)



Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

One CANNOT compute (or generate from logic) a truly random number.
Now, quasi-random number generators are a dime a dozen, like you imply.



There are lots of digital chips, including some Intel processors, that
have cryptographic-grade random number generators on-chip. One common
technique is to use a bunch of asynchronous ring oscillators to
scramble pseudo-random shift registers. Lots of references on the web.

I have a technique that uses an i/o pin as a noisy/chaotic RC ramp
generator. Fun, but essentially useless.

John

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On Sun, 24 Oct 2010 00:45:57 -0400, "Michael A. Terrell"
wrote:


John Larkin wrote:

On Fri, 22 Oct 2010 00:53:55 -0400, "Michael A. Terrell"
wrote:


Jim Thompson wrote:

I'd like to conjure up a random bit generator.

Just feed it a clock and have it generate random bits.

74HC... components preferred... I have most everything in that family
in my parts bin ;-)


XOR some of Sloman's messages. ;-)


Those aren't very random. He keeps saying the same stuff, over and
over.



If you XOR enough of them, the typos add up into a random mess.


Good point.

John

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