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RSA

Section: User Contributed Perl Documentation (3)
Updated: 2025-10-30
Index

NAME

Crypt::OpenSSL::RSA - RSA encoding and decoding, using the openSSL libraries

SYNOPSIS

  use Crypt::OpenSSL::Random;  use Crypt::OpenSSL::RSA;  # not necessary if we have /dev/random:  Crypt::OpenSSL::Random::random_seed($good_entropy);  Crypt::OpenSSL::RSA->import_random_seed();  $rsa_pub = Crypt::OpenSSL::RSA->new_public_key($key_string);  $ciphertext = $rsa->encrypt($plaintext);  $rsa_priv = Crypt::OpenSSL::RSA->new_private_key($key_string);  $plaintext = $rsa->decrypt($ciphertext);  $rsa = Crypt::OpenSSL::RSA->generate_key(1024); # or  $rsa = Crypt::OpenSSL::RSA->generate_key(1024, $prime);  print "private key is:\n", $rsa->get_private_key_string();  print "public key (in PKCS1 format) is:\n",        $rsa->get_public_key_string();  print "public key (in X509 format) is:\n",        $rsa->get_public_key_x509_string();  $rsa_priv->use_md5_hash(); # insecure. use_sha256_hash or use_sha1_hash are the default  $signature = $rsa_priv->sign($plaintext);  print "Signed correctly\n" if ($rsa->verify($plaintext, $signature));

SECURITY

Version 0.35 makes the use of PKCS#1 v1.5 padding a fatal error. It isvery difficult to implement PKCS#1 v1.5 padding securely. If you are stillusing RSA in in general, you should be looking at alternative encryptionalgorithms.

DESCRIPTION

"Crypt::OpenSSL::RSA" provides the ability to RSA encrypt strings which aresomewhat shorter than the block size of a key. It also allows for decryption,signatures and signature verification.

NOTE: Many of the methods in this package can croak, so use "eval", orError.pm's try/catch mechanism to capture errors. Also, while somemethods from earlier versions of this package return true on success,this (never documented) behavior is no longer the case.

Class Methods

new_public_key

Create a new "Crypt::OpenSSL::RSA" object by loading a public key infrom a string containing Base64/DER-encoding of either the PKCS1 orX.509 representation of the key. The string should include the"-----BEGIN...-----" and "-----END...-----" lines.

The padding is set to PKCS1_OAEP, but can be changed with the"use_xxx_padding" methods.

new_private_key

Create a new "Crypt::OpenSSL::RSA" object by loading a private key infrom an string containing the Base64/DER encoding of the PKCS1representation of the key. The string should include the"-----BEGIN...-----" and "-----END...-----" lines. The padding is set toPKCS1_OAEP, but can be changed with "use_xxx_padding".

An optional parameter can be passed for passphase protected private key:

passphase: The passphase which protects the private key.

generate_key

Create a new "Crypt::OpenSSL::RSA" object by constructing aprivate/public key pair. The first (mandatory) argument is the keysize, while the second optional argument specifies the public exponent(the default public exponent is 65537). The padding is set to"PKCS1_OAEP", but can be changed with use_xxx_padding methods.

new_key_from_parameters

Given Crypt::OpenSSL::Bignum objects for n, e, and optionally d, p,and q, where p and q are the prime factors of n, e is the publicexponent and d is the private exponent, create a newCrypt::OpenSSL::RSA object using these values. If p and q areprovided and d is undef, d is computed. Note that while p and q arenot necessary for a private key, their presence will speed upcomputation.

import_random_seed

Import a random seed from Crypt::OpenSSL::Random, since the OpenSSLlibraries won't allow sharing of random structures across perl XSmodules.

Instance Methods

DESTROY

Clean up after ourselves. In particular, erase and free the memoryoccupied by the RSA key structure.

get_public_key_string

Return the Base64/DER-encoded PKCS1 representation of the publickey. This string hasheader and footer lines:

  -----BEGIN RSA PUBLIC KEY------  -----END RSA PUBLIC KEY------

get_public_key_x509_string

Return the Base64/DER-encoded representation of the "subjectpublic key", suitable for use in X509 certificates. This string hasheader and footer lines:

  -----BEGIN PUBLIC KEY------  -----END PUBLIC KEY------

and is the format that is produced by running "openssl rsa -pubout".

get_private_key_string

Return the Base64/DER-encoded PKCS1 representation of the privatekey. This string hasheader and footer lines:

  -----BEGIN RSA PRIVATE KEY------  -----END RSA PRIVATE KEY------

2 optional parameters can be passed for passphase protected private keystring:

passphase: The passphase which protects the private key.
cipher name: The cipher algorithm used to protect the private key. Default to'des3'.

encrypt

Encrypt a binary "string" using the public (portion of the) key.

decrypt

Decrypt a binary "string". Croaks if the key is public only.

private_encrypt

Encrypt a binary "string" using the private key. Croaks if the key ispublic only.

public_decrypt

Decrypt a binary "string" using the public (portion of the) key.

sign

Sign a string using the secret (portion of the) key.

verify

Check the signature on a text.

use_no_padding

Use raw RSA encryption. This mode should only be used to implementcryptographically sound padding modes in the application code.Encrypting user data directly with RSA is insecure.

use_pkcs1_padding

PKCS #1 v1.5 padding has been disabled as it is nearly impossible to use thispadding method in a secure manner. It is known to be vulnerable to timingbased side channel attacks. use_pkcs1_padding() results in a fatal error.

Marvin Attack <https://github.com/tomato42/marvin-toolkit/blob/master/README.md>

use_pkcs1_oaep_padding

Use "EME-OAEP" padding as defined in PKCS #1 v2.0 with SHA-1, MGF1 andan empty encoding parameter. This mode of padding is recommended forall new applications. It is the default mode used by"Crypt::OpenSSL::RSA".

use_pkcs1_pss_padding

Use "RSA-PSS" padding as defined in PKCS#1 v2.1. In general, RSA-PSSshould be used as a replacement for RSA-PKCS#1 v1.5. The module specifiesthe message digest being requested and the appropriate mgf1 setting andsalt length for the digest.

Note: RSA-PSS cannot be used for encryption/decryption and results in afatal error. Call "use_pkcs1_oaep_padding" for encryption operations.

use_sslv23_padding

Use "PKCS #1 v1.5" padding with an SSL-specific modification thatdenotes that the server is SSL3 capable.

Not available since OpenSSL 3.

use_md5_hash

Use the RFC 1321 MD5 hashing algorithm by Ron Rivest when signing andverifying messages.

Note that this is considered insecure.

use_sha1_hash

Use the RFC 3174 Secure Hashing Algorithm (FIPS 180-1) when signingand verifying messages. This is the default, when use_sha256_hash isnot available.

use_sha224_hash, use_sha256_hash, use_sha384_hash, use_sha512_hash

These FIPS 180-2 hash algorithms, for use when signing and verifyingmessages, are only available with newer openssl versions (>= 0.9.8).

use_sha256_hash is the default hash mode when available.

use_ripemd160_hash

Dobbertin, Bosselaers and Preneel's RIPEMD hashing algorithm whensigning and verifying messages.

use_whirlpool_hash

Vincent Rijmen und Paulo S. L. M. Barreto ISO/IEC 10118-3:2004WHIRLPOOL hashing algorithm when signing and verifying messages.

size

Returns the size, in bytes, of the key. All encrypted text will be ofthis size, and depending on the padding mode used, the length ofthe text to be encrypted should be:

pkcs1_oaep_padding: at most 42 bytes less than this size.
pkcs1_padding or sslv23_padding: at most 11 bytes less than this size.
no_padding: exactly this size.

check_key

This function validates the RSA key, returning a true value if the keyis valid, and a false value otherwise. Croaks if the key is public only.

get_key_parameters

Return "Crypt::OpenSSL::Bignum" objects representing the values of "n","e", "d", "p", "q", "d mod (p-1)", "d mod (q-1)", and "1/q mod p",where "p" and "q" are the prime factors of "n", "e" is the publicexponent and "d" is the private exponent. Some of these values may returnas "undef"; only "n" and "e" will be defined for a public key. The"Crypt::OpenSSL::Bignum" module must be installed for this to work.

is_private

Return true if this is a private key, and false if it is private only.

BUGS

There is a small memory leak when generating new keys of more than 512 bits.

AUTHOR

Ian Robertson, "irobertsAATTcpan.org". For support, please email"perl-openssl-usersAATTlists.sourceforge.net".

ACKNOWLEDGEMENTS

LICENSE

This document was created byman2html,using the manual pages.

RSA