Otdfbt

Will a top journal at least read my introduction?

How can I practically buy stocks?

Phrase for the opposite of "foolproof"

Why is it that the natural deduction method can't test for invalidity?

Do I have an "anti-research" personality?

How to make a pipeline wait for end-of-file or stop after an error?

French for 'It must be my imagination'?

How to creep the reader out with what seems like a normal person?

What do the phrase "Reeyan's seacrest" and the word "fraggle" mean in a sketch?

Packing rectangles: Does rotation ever help?

How to verbalise code in Mathematica?

Reducing vertical space in stackrel

How much cash can I safely carry into the USA and avoid civil forfeiture?

Which big number is bigger?

simple conditions equation

Sci-fi book: portals appear in London and send a failed artist towards a designated path where he operate a giant superweapon

Mac Pro install disk keeps ejecting itself

Sci-fi novel series with instant travel between planets through gates. A river runs through the gates

What route did the Hindenburg take when traveling from Germany to the U.S.?

Binary Numbers Magic Trick

Don’t seats that recline flat defeat the purpose of having seatbelts?

How do I use proper grammar in the negation of "have not" for the following sentence translation?

How to pronounce 'C++' in Spanish

a sore throat vs a strep throat vs strep throat

Is openssl rand command cryptographically secure?

Can a PRNG with a fixed amount of entropy always be detected?What stops the Multiply-With-Carry RNG from being a Cryptographically Secure PRNG?Is a Mersenne-twister cryptographically secure if I truncate the output?How Brittle Are LCG-Cracking Techniques?ECC considered secure in OpenSSL?Is this JS library using openssl genrsa -rand improperly?Cryptographic random numbers for key generationLink between openssl 'req' command and 'unable to get local issuer certificate'?openssl command line equivalent of AESWrap? (defined in RFC3394; use in AmazonS3 Client Side Encryption of datakey wrapping)The “openssl genrsa” command only generates a private key?

5

1

$begingroup$

I'm wondering if the openssl rand command produces cryptographically secure random bytes. For example when in need for a random password or token:

openssl rand -hex 32

The man page unfortunately does neither state it's cryptographically secure, nor that it's not.

On the one hand, I think this is openssl, its sole purpose is to do cryptography. On the other hand, the man page states something about reading and writing seed data instead of directly querying a CSPRNG.

So it is somewhat unclear for the end user. Does someone know?

random-number-generator openssl

share|improve this question

asked Apr 20 at 14:51

firefexxfirefexx

1624

$endgroup$

add a comment | 

5

1

$begingroup$

I'm wondering if the openssl rand command produces cryptographically secure random bytes. For example when in need for a random password or token:

openssl rand -hex 32

The man page unfortunately does neither state it's cryptographically secure, nor that it's not.

On the one hand, I think this is openssl, its sole purpose is to do cryptography. On the other hand, the man page states something about reading and writing seed data instead of directly querying a CSPRNG.

So it is somewhat unclear for the end user. Does someone know?

random-number-generator openssl

share|improve this question

asked Apr 20 at 14:51

firefexxfirefexx

1624

$endgroup$

add a comment | 

$begingroup$

I'm wondering if the openssl rand command produces cryptographically secure random bytes. For example when in need for a random password or token:

openssl rand -hex 32

The man page unfortunately does neither state it's cryptographically secure, nor that it's not.

On the one hand, I think this is openssl, its sole purpose is to do cryptography. On the other hand, the man page states something about reading and writing seed data instead of directly querying a CSPRNG.

So it is somewhat unclear for the end user. Does someone know?

random-number-generator openssl

share|improve this question

asked Apr 20 at 14:51

firefexxfirefexx

1624

$endgroup$

openssl rand -hex 32

share|improve this question

asked Apr 20 at 14:51

firefexxfirefexx

1624

share|improve this question

asked Apr 20 at 14:51

firefexxfirefexx

1624

asked Apr 20 at 14:51

firefexxfirefexx

1624

asked Apr 20 at 14:51

firefexxfirefexx

1624

1 Answer
1

active

oldest

votes

5

$begingroup$

Yes, it is cryptographically secure, pseudo random output, seeded by retrieving secure random data from the operating system.

If it is random or not depends on the fact if the OS RNG is random. This is usually the case on normal desktops, but you'd better be sure for e.g. limited embedded systems. If no truly random data can be retrieved - according to RAND_bytes - then rand will exit with an error.

---

Any random source that you add using -rand [file][:file]* is used as additional seed data - in other words, the output will always be random, even if you supply the same seed.

As the pseudo random generator provided by OpenSSL generally runs in the application space on the main thread, it may be faster than asking a lot of data from /dev/urandom. But to be honest, most of the time using /dev/urandom suffices (and current implementations are pretty fast as well).

---

You can see that it is random when you look at the link to the RAND_bytes manual page which is the function that lies behind command line rand and is linked to from the manual page (in the "see also section, but yeah"):

RAND_bytes() puts num cryptographically strong pseudo-random bytes into buf. An error occurs if the PRNG has not been seeded with enough randomness to ensure an unpredictable byte sequence.

That RAND_bytes() is used can be found in the source file for the rand command, rand.c, so yes, this is indeed the function that is called.

share|improve this answer

edited Apr 20 at 17:09

answered Apr 20 at 16:18

Maarten Bodewes♦Maarten Bodewes

56.3k679197

$endgroup$

add a comment | 

Your Answer

StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "281"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);

else
createEditor();

);

function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);



);

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);

Sign up using Google

Sign up using Facebook

Sign up using Email and Password

Post as a guest

Name

Email

Required, but never shown

StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fcrypto.stackexchange.com%2fquestions%2f68919%2fis-openssl-rand-command-cryptographically-secure%23new-answer', 'question_page');

);

Post as a guest

Name

Email

Required, but never shown

5

$begingroup$

Yes, it is cryptographically secure, pseudo random output, seeded by retrieving secure random data from the operating system.

If it is random or not depends on the fact if the OS RNG is random. This is usually the case on normal desktops, but you'd better be sure for e.g. limited embedded systems. If no truly random data can be retrieved - according to RAND_bytes - then rand will exit with an error.

---

Any random source that you add using -rand [file][:file]* is used as additional seed data - in other words, the output will always be random, even if you supply the same seed.

As the pseudo random generator provided by OpenSSL generally runs in the application space on the main thread, it may be faster than asking a lot of data from /dev/urandom. But to be honest, most of the time using /dev/urandom suffices (and current implementations are pretty fast as well).

---

You can see that it is random when you look at the link to the RAND_bytes manual page which is the function that lies behind command line rand and is linked to from the manual page (in the "see also section, but yeah"):

RAND_bytes() puts num cryptographically strong pseudo-random bytes into buf. An error occurs if the PRNG has not been seeded with enough randomness to ensure an unpredictable byte sequence.

That RAND_bytes() is used can be found in the source file for the rand command, rand.c, so yes, this is indeed the function that is called.

share|improve this answer

edited Apr 20 at 17:09

answered Apr 20 at 16:18

Maarten Bodewes♦Maarten Bodewes

56.3k679197

$endgroup$

add a comment | 

5

$begingroup$

Yes, it is cryptographically secure, pseudo random output, seeded by retrieving secure random data from the operating system.

If it is random or not depends on the fact if the OS RNG is random. This is usually the case on normal desktops, but you'd better be sure for e.g. limited embedded systems. If no truly random data can be retrieved - according to RAND_bytes - then rand will exit with an error.

---

Any random source that you add using -rand [file][:file]* is used as additional seed data - in other words, the output will always be random, even if you supply the same seed.

As the pseudo random generator provided by OpenSSL generally runs in the application space on the main thread, it may be faster than asking a lot of data from /dev/urandom. But to be honest, most of the time using /dev/urandom suffices (and current implementations are pretty fast as well).

---

You can see that it is random when you look at the link to the RAND_bytes manual page which is the function that lies behind command line rand and is linked to from the manual page (in the "see also section, but yeah"):

RAND_bytes() puts num cryptographically strong pseudo-random bytes into buf. An error occurs if the PRNG has not been seeded with enough randomness to ensure an unpredictable byte sequence.

That RAND_bytes() is used can be found in the source file for the rand command, rand.c, so yes, this is indeed the function that is called.

share|improve this answer

edited Apr 20 at 17:09

answered Apr 20 at 16:18

Maarten Bodewes♦Maarten Bodewes

56.3k679197

$endgroup$

add a comment | 

$begingroup$

Yes, it is cryptographically secure, pseudo random output, seeded by retrieving secure random data from the operating system.

If it is random or not depends on the fact if the OS RNG is random. This is usually the case on normal desktops, but you'd better be sure for e.g. limited embedded systems. If no truly random data can be retrieved - according to RAND_bytes - then rand will exit with an error.

---

Any random source that you add using -rand [file][:file]* is used as additional seed data - in other words, the output will always be random, even if you supply the same seed.

As the pseudo random generator provided by OpenSSL generally runs in the application space on the main thread, it may be faster than asking a lot of data from /dev/urandom. But to be honest, most of the time using /dev/urandom suffices (and current implementations are pretty fast as well).

---

You can see that it is random when you look at the link to the RAND_bytes manual page which is the function that lies behind command line rand and is linked to from the manual page (in the "see also section, but yeah"):

RAND_bytes() puts num cryptographically strong pseudo-random bytes into buf. An error occurs if the PRNG has not been seeded with enough randomness to ensure an unpredictable byte sequence.

That RAND_bytes() is used can be found in the source file for the rand command, rand.c, so yes, this is indeed the function that is called.

share|improve this answer

edited Apr 20 at 17:09

answered Apr 20 at 16:18

Maarten Bodewes♦Maarten Bodewes

56.3k679197

$endgroup$

share|improve this answer

edited Apr 20 at 17:09

answered Apr 20 at 16:18

Maarten Bodewes♦Maarten Bodewes

56.3k679197

answered Apr 20 at 16:18

Maarten Bodewes♦Maarten Bodewes

56.3k679197

answered Apr 20 at 16:18

Maarten Bodewes♦Maarten Bodewes

56.3k679197