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I have a private key file and I want to encrypt

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4

When I use openssl genrsa -out yourdomain.key 2048 command to generate a key. I understand the yourdomain.key file contains both the private and public keys. But when I check the content of this key file, it starts and ends with -----BEGIN PRIVATE KEY----- and -----END PRIVATE KEY-----, which gives feeling that this file is just private key. Why is that? This makes me very confused.

If I want to encrypt a message using private key, so I apply the entire yourdomain.key key? Or should I extract the private key part from it and use that?

cryptography openssl asymmetric

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4

When I use openssl genrsa -out yourdomain.key 2048 command to generate a key. I understand the yourdomain.key file contains both the private and public keys. But when I check the content of this key file, it starts and ends with -----BEGIN PRIVATE KEY----- and -----END PRIVATE KEY-----, which gives feeling that this file is just private key. Why is that? This makes me very confused.

If I want to encrypt a message using private key, so I apply the entire yourdomain.key key? Or should I extract the private key part from it and use that?

cryptography openssl asymmetric

share|improve this question

edited 9 hours ago

Gilles

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asked 9 hours ago

ZhenZhen

2411 bronze badge

New contributor

Zhen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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add a comment
 | 

When I use openssl genrsa -out yourdomain.key 2048 command to generate a key. I understand the yourdomain.key file contains both the private and public keys. But when I check the content of this key file, it starts and ends with -----BEGIN PRIVATE KEY----- and -----END PRIVATE KEY-----, which gives feeling that this file is just private key. Why is that? This makes me very confused.

If I want to encrypt a message using private key, so I apply the entire yourdomain.key key? Or should I extract the private key part from it and use that?

cryptography openssl asymmetric

share|improve this question

edited 9 hours ago

Gilles

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asked 9 hours ago

ZhenZhen

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Zhen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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edited 9 hours ago

Gilles

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asked 9 hours ago

ZhenZhen

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edited 9 hours ago

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edited 9 hours ago

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2 Answers
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6

Do not use the OpenSSL command line to encrypt or sign anything. The OpenSSL command line is a debugging tool. To encrypt or sign a message, use a tool designed for this purpose, such as GPG.

A private key file contains all the information needed to construct the public key. If you have a private key in a format that OpenSSL understands and you want to get the corresponding public key, you can use openssl pkey -pubout …. But that's not the format GPG needs. GPG generates its own keys.

share|improve this answer

answered 9 hours ago

GillesGilles

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2

The private key is used to decrypt, and to sign things. You don't use it to encrypt. You use the public key for that. But openssl genrsa will not generate the public key, only the private. To encrypt things, you must first generate the public key (so you have a keypair: private and public):

openssl rsa -in yourdomain.key -outform PEM -pubout -out public.pem

This will create public.pem file with, well, the public key. Use it to encript the file:

openssl rsautl -encrypt -inkey public.pem -pubin -in file.txt -out file.enc

To decrypt later, you use the private key:

openssl rsautl -decrypt -inkey yourdomain.key -in file.enc -out file.dec

share|improve this answer

edited 48 mins ago

Benoit Esnard

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answered 9 hours ago

ThoriumBRThoriumBR

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• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  what do you think signing is if not encrypting information? Related: security.stackexchange.com/questions/9957/…
  
  – eis
  6 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  but in general, of course, you're correct, and this answer is probably what OP needs
  
  – eis
  4 mins ago
  

  
  
  
  

add a comment
 | 

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6

Do not use the OpenSSL command line to encrypt or sign anything. The OpenSSL command line is a debugging tool. To encrypt or sign a message, use a tool designed for this purpose, such as GPG.

A private key file contains all the information needed to construct the public key. If you have a private key in a format that OpenSSL understands and you want to get the corresponding public key, you can use openssl pkey -pubout …. But that's not the format GPG needs. GPG generates its own keys.

share|improve this answer

answered 9 hours ago

GillesGilles

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add a comment
 | 

6

Do not use the OpenSSL command line to encrypt or sign anything. The OpenSSL command line is a debugging tool. To encrypt or sign a message, use a tool designed for this purpose, such as GPG.

A private key file contains all the information needed to construct the public key. If you have a private key in a format that OpenSSL understands and you want to get the corresponding public key, you can use openssl pkey -pubout …. But that's not the format GPG needs. GPG generates its own keys.

share|improve this answer

answered 9 hours ago

GillesGilles

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add a comment
 | 

Do not use the OpenSSL command line to encrypt or sign anything. The OpenSSL command line is a debugging tool. To encrypt or sign a message, use a tool designed for this purpose, such as GPG.

A private key file contains all the information needed to construct the public key. If you have a private key in a format that OpenSSL understands and you want to get the corresponding public key, you can use openssl pkey -pubout …. But that's not the format GPG needs. GPG generates its own keys.

share|improve this answer

answered 9 hours ago

GillesGilles

41.6k1212 gold badges100100 silver badges155155 bronze badges

share|improve this answer

answered 9 hours ago

GillesGilles

41.6k1212 gold badges100100 silver badges155155 bronze badges

answered 9 hours ago

GillesGilles

41.6k1212 gold badges100100 silver badges155155 bronze badges

answered 9 hours ago

GillesGilles

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2

The private key is used to decrypt, and to sign things. You don't use it to encrypt. You use the public key for that. But openssl genrsa will not generate the public key, only the private. To encrypt things, you must first generate the public key (so you have a keypair: private and public):

openssl rsa -in yourdomain.key -outform PEM -pubout -out public.pem

This will create public.pem file with, well, the public key. Use it to encript the file:

openssl rsautl -encrypt -inkey public.pem -pubin -in file.txt -out file.enc

To decrypt later, you use the private key:

openssl rsautl -decrypt -inkey yourdomain.key -in file.enc -out file.dec

share|improve this answer

edited 48 mins ago

Benoit Esnard

11.4k77 gold badges5656 silver badges5959 bronze badges

answered 9 hours ago

ThoriumBRThoriumBR

28k88 gold badges6868 silver badges8686 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  what do you think signing is if not encrypting information? Related: security.stackexchange.com/questions/9957/…
  
  – eis
  6 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  but in general, of course, you're correct, and this answer is probably what OP needs
  
  – eis
  4 mins ago
  

  
  
  
  

add a comment
 | 

2

The private key is used to decrypt, and to sign things. You don't use it to encrypt. You use the public key for that. But openssl genrsa will not generate the public key, only the private. To encrypt things, you must first generate the public key (so you have a keypair: private and public):

openssl rsa -in yourdomain.key -outform PEM -pubout -out public.pem

This will create public.pem file with, well, the public key. Use it to encript the file:

openssl rsautl -encrypt -inkey public.pem -pubin -in file.txt -out file.enc

To decrypt later, you use the private key:

openssl rsautl -decrypt -inkey yourdomain.key -in file.enc -out file.dec

share|improve this answer

edited 48 mins ago

Benoit Esnard

11.4k77 gold badges5656 silver badges5959 bronze badges

answered 9 hours ago

ThoriumBRThoriumBR

28k88 gold badges6868 silver badges8686 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  what do you think signing is if not encrypting information? Related: security.stackexchange.com/questions/9957/…
  
  – eis
  6 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  but in general, of course, you're correct, and this answer is probably what OP needs
  
  – eis
  4 mins ago
  

  
  
  
  

add a comment
 | 

The private key is used to decrypt, and to sign things. You don't use it to encrypt. You use the public key for that. But openssl genrsa will not generate the public key, only the private. To encrypt things, you must first generate the public key (so you have a keypair: private and public):

openssl rsa -in yourdomain.key -outform PEM -pubout -out public.pem

This will create public.pem file with, well, the public key. Use it to encript the file:

openssl rsautl -encrypt -inkey public.pem -pubin -in file.txt -out file.enc

To decrypt later, you use the private key:

openssl rsautl -decrypt -inkey yourdomain.key -in file.enc -out file.dec

share|improve this answer

edited 48 mins ago

Benoit Esnard

11.4k77 gold badges5656 silver badges5959 bronze badges

answered 9 hours ago

ThoriumBRThoriumBR

28k88 gold badges6868 silver badges8686 bronze badges

openssl rsa -in yourdomain.key -outform PEM -pubout -out public.pem

openssl rsautl -encrypt -inkey public.pem -pubin -in file.txt -out file.enc

openssl rsautl -decrypt -inkey yourdomain.key -in file.enc -out file.dec

share|improve this answer

edited 48 mins ago

Benoit Esnard

11.4k77 gold badges5656 silver badges5959 bronze badges

answered 9 hours ago

ThoriumBRThoriumBR

28k88 gold badges6868 silver badges8686 bronze badges

edited 48 mins ago

Benoit Esnard

11.4k77 gold badges5656 silver badges5959 bronze badges

edited 48 mins ago

Benoit Esnard

11.4k77 gold badges5656 silver badges5959 bronze badges

answered 9 hours ago

ThoriumBRThoriumBR

28k88 gold badges6868 silver badges8686 bronze badges

answered 9 hours ago

ThoriumBRThoriumBR

28k88 gold badges6868 silver badges8686 bronze badges