5 openssl-glossary - An OpenSSL Glossary
9 =for comment Please keep the items in case-insensitive alphabetical order
15 Cryptograpic primitives such as the SHA256 digest, or AES encryption are
16 referred to in OpenSSL as "algorithms". There can be more than one
17 implementation for any given algorithm available for use.
23 ASN.1 ("Abstract Syntax Notation One") is a notation for describing abstract
24 types and values. It is defined in the ITU-T documents X.680 to X.683:
26 L<https://www.itu.int/rec/T-REC-X.680>,
27 L<https://www.itu.int/rec/T-REC-X.681>,
28 L<https://www.itu.int/rec/T-REC-X.682>,
29 L<https://www.itu.int/rec/T-REC-X.683>
33 An OpenSSL Provider that contains encoders and decoders for OpenSSL keys. All
34 the algorithm implementations in the Base Provider are also available in the
37 L<OSSL_PROVIDER-base(7)>
41 A decoder is a type of algorithm used for decoding keys and parameters from some
42 external format such as PEM or DER.
44 L<OSSL_DECODER_CTX_new_for_pkey(3)>
46 =item Default Provider
48 An OpenSSL Provider that contains the most commmon OpenSSL algorithm
49 implementations. It is loaded by default if no other provider is available. All
50 the algorithm implementations in the Base Provider are also available in the
53 L<OSSL_PROVIDER-default(7)>
55 =item DER ("Distinguished Encoding Rules")
57 DER is a binary encoding of data, structured according to an ASN.1
58 specification. This is a common encoding used for cryptographic objects
59 such as private and public keys, certificates, CRLs, ...
61 It is defined in ITU-T document X.690:
63 L<https://www.itu.int/rec/T-REC-X.690>
67 An encoder is a type of algorithm used for encoding keys and parameters to some
68 external format such as PEM or DER.
70 L<OSSL_ENCODER_CTX_new_for_pkey(3)>
72 =item Explicit Fetching
74 Explicit Fetching is a type of Fetching (see Fetching). Explicit Fetching is
75 where a function call is made to obtain an algorithm object representing an
76 implementation such as L<EVP_MD_fetch(3)> or L<EVP_CIPHER_fetch(3)>
80 Fetching is the process of looking through the available algorithm
81 implementations, applying selection criteria (via a property query string), and
82 finally choosing the implementation that will be used.
84 Also see Explicit Fetching and Implict Fetching.
90 An OpenSSL Provider that contains OpenSSL algorithm implementations that have
91 been validated according to the FIPS 140-2 standard.
93 L<OSSL_PROVIDER-FIPS(7)>
95 =item Implicit Fetching
97 Implicit Fetching is a type of Fetching (see Fetching). Implicit Fetching is
98 where an algorithm object with no associated implementation is used such as the
99 return value from L<EVP_sha256(3)> or L<EVP_aes_128_cbc(3)>. With implicit
100 fetching an implementation is fetched automatically using default selection
101 criteria the first time the algorithm is used.
103 =item Legacy Provider
105 An OpenSSL Provider that contains algorithm implementations that are considered
106 insecure or are no longer in common use.
108 L<OSSL_PROVIDER-legacy(7)>
110 =item Library Context
112 A Library Context in OpenSSL is represented by the type B<OSSL_LIB_CTX>. It can
113 be thought of as a scope within which configuration options apply. If an
114 application does not explicitly create a library context then the "default"
115 one is used. Many OpenSSL functions can take a library context as an argument.
116 A NULL value can always be passed to indicate the default library context.
122 MSBLOB is a Microsoft specific binary format for RSA and DSA keys, both
123 private and public. This form is never passphrase protected.
127 An OpenSSL Provider that contains no algorithm implementations. This can be
128 useful to prevent the default provider from being automatically loaded in a
131 L<OSSL_PROVIDER-null(7)>
135 An operation is a group of OpenSSL functions with a common purpose such as
136 encryption, or digesting.
140 =item PEM ("Privacy Enhanced Message")
142 PEM is a format used for encoding of binary content into a mail and ASCII
143 friendly form. The content is a series of base64-encoded lines, surrounded
144 by begin/end markers each on their own line. For example:
146 -----BEGIN PRIVATE KEY-----
149 -----END PRIVATE KEY-----
151 Optional header line(s) may appear after the begin line, and their existence
152 depends on the type of object being written or read.
154 For all OpenSSL uses, the binary content is expected to be a DER encoded
157 This is defined in IETF RFC 1421:
159 L<https://tools.ietf.org/html/rfc1421>
163 PKCS#8 is a specification of ASN.1 structures that OpenSSL uses for storing
164 or transmitting any private key in a key type agnostic manner.
165 There are two structures worth noting for OpenSSL use, one that contains the
166 key data in unencrypted form (known as "PrivateKeyInfo") and an encrypted
167 wrapper structure (known as "EncryptedPrivateKeyInfo").
169 This is specified in RFC 5208:
171 L<https://tools.ietf.org/html/rfc5208>
175 A property is a way of classifying and selecting algorithm implementations.
176 A property is a key/value pair expressed as a string. For example all algorithm
177 implementations in the default provider have the property "provider=default".
178 An algorithm implementation can have multiple properties defined against it.
180 Also see Property Query String.
184 =item Property Query String
186 A property query string is a string containing a sequence of properties that
187 can be used to select an algorithm implementation. For example the query string
188 "provider=example,foo=bar" will select algorithms from the "example" provider
189 that have a "foo" property defined for them with a value of "bar".
191 Property Query Strings are used during fetching. See Fetching.
197 A provider in OpenSSL is a component that groups together algorithm
198 implementations. Providers can come from OpenSSL itself or from third parties.
204 PVK is a Microsoft specific binary format for RSA and DSA private keys.
205 This form may be passphrase protected.
207 =item SubjectPublicKeyInfo
209 SubjectPublicKeyInfo is an ASN.1 structure that OpenSSL uses for storing and
210 transmitting any public key in a key type agnostic manner.
212 This is specified as part of the specification for certificates, RFC 5280:
214 L<https://tools.ietf.org/html/rfc5280>
220 This glossary was added in OpenSSL 3.0.
224 Copyright 2020-2021 The OpenSSL Project Authors. All Rights Reserved.
226 Licensed under the Apache License 2.0 (the "License"). You may not use
227 this file except in compliance with the License. You can obtain a copy
228 in the file LICENSE in the source distribution or at
229 L<https://www.openssl.org/source/license.html>.