RSA Public Key Importer and Exporter

An importer and exporter for the ASN.1 DER encoding of an RSA public key.

This project includes the RSAPublicKeyImporter and RSAPublicKeyExporter module, written in Swift and featuring an importer and exporter that can be used for converting the ASN.1 DER encoding of an RSA public key from and to a format typically used by tools and programming languages outside the Apple ecosystem (e.g. OpenSSL, Java, PHP and Perl).

Note that built-in support for both encoding formats is actually quite solid in the Apple ecosystem, meaning that the RSAPublicKeyImporter module is kind of redundant in that sense. However, this module can be used for testing the RSAPublicKeyExporter module that has a real-world application (or at least as long as Apple has no built-in support for exporting RSA public keys). In any case, both modules are considered a basic example of how the SimpleASN1Reader and SimpleASN1Writer module in the simple-asn1-reader-writer project can be used.

Usage

rsa-public-key-importer-exporter is a SwiftPM project and can be built, tested and run using these commands:

$ swift build
$ swift test
$ swift run RSAPublicKeyImportExportDemo

To depend on rsa-public-key-importer-exporter, put the following in the dependencies of your Package.swift:

.package(url: "https://github.com/nextincrement/rsa-public-key-importer-exporter.git", from: "0.1.0"),

Code Examples:

import RSAPublicKeyImporter

[...]

let subjectPublicKeyInfoData = [...]

let rsaPublicKeyData = try RSAPublicKeyImporter().fromSubjectPublicKeyInfo(subjectPublicKeyInfoData)

import RSAPublicKeyExporter

[...]

let rsaPublicKeyData = [...]

let subjectPublicKeyInfoData = RSAPublicKeyExporter().toSubjectPublicKeyInfo(rsaPublicKeyData)

Using the RSAPublicKeyImporter and RSAPublicKeyExporter Together

Create a public key (for example by using OpenSSL):

$ openssl genrsa -out key.pem 2048
$ openssl rsa -in key.pem -outform PEM -pubout -out public.pem

Extract the Base64 encoded DER encoding from the key.pem file, paste it in this file (or simply keep the example key unchanged) and run the demo:

$ swift run RSAPublicKeyImportExportDemo

Expected output:

X.509 encoded RSA public key as a Base64 string:
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA3o1GZDe0ivcgcWetu82mX+G7G5P9Ztsq5xptSmzL36mfyxUjrctA2MCY
0n604s5Gmv3hrrYgUiRndhmITPngnXiKUst+CV4uWEcwqe3qHRfrTXcCMhsOLd8OPmOkOHlsXwwM1OOGnHeQd5bRkCt43haSMrv5
5LeHH7JRo7+d9b08G04Ih1PAHzQCgfkwgJK+M5fU0k+sP4qeKcj3iFanGkCkl0eVcVbEoW7E9dQfg1VBT+DKbioW3xImBc2Rw+fo
2j2gPVNKqvYGXEj3INvEgPxNtqk4DJ4DC+1FyYu94XM/qEVUQ8fKX0kzmDoDQ2WCFBbzO+yCLqpMiscgBH9XpwIDAQAB

...same X.509 encoded RSA public key as an array of hex values:
30 82 01 22 30 0d 06 09 2a 86 48 86 f7 0d 01 01 01 05 00 03 82 01 0f 00 30 82 01 0a 02 82 01 01 00
de 8d 46 64 37 b4 8a f7 20 71 67 ad bb cd a6 5f e1 bb 1b 93 fd 66 db 2a e7 1a 6d 4a 6c cb df a9 9f
cb 15 23 ad cb 40 d8 c0 98 d2 7e b4 e2 ce 46 9a fd e1 ae b6 20 52 24 67 76 19 88 4c f9 e0 9d 78 8a
52 cb 7e 09 5e 2e 58 47 30 a9 ed ea 1d 17 eb 4d 77 02 32 1b 0e 2d df 0e 3e 63 a4 38 79 6c 5f 0c 0c
d4 e3 86 9c 77 90 77 96 d1 90 2b 78 de 16 92 32 bb f9 e4 b7 87 1f b2 51 a3 bf 9d f5 bd 3c 1b 4e 08
87 53 c0 1f 34 02 81 f9 30 80 92 be 33 97 d4 d2 4f ac 3f 8a 9e 29 c8 f7 88 56 a7 1a 40 a4 97 47 95
71 56 c4 a1 6e c4 f5 d4 1f 83 55 41 4f e0 ca 6e 2a 16 df 12 26 05 cd 91 c3 e7 e8 da 3d a0 3d 53 4a
aa f6 06 5c 48 f7 20 db c4 80 fc 4d b6 a9 38 0c 9e 03 0b ed 45 c9 8b bd e1 73 3f a8 45 54 43 c7 ca
5f 49 33 98 3a 03 43 65 82 14 16 f3 3b ec 82 2e aa 4c 8a c7 20 04 7f 57 a7 02 03 01 00 01

Result of a call to the fromSubjectPublicKeyInfo(_:) function as an array of hex values:
30 82 01 0a 02 82 01 01 00 de 8d 46 64 37 b4 8a f7 20 71 67 ad bb cd a6 5f e1 bb 1b 93 fd 66 db 2a
e7 1a 6d 4a 6c cb df a9 9f cb 15 23 ad cb 40 d8 c0 98 d2 7e b4 e2 ce 46 9a fd e1 ae b6 20 52 24 67
76 19 88 4c f9 e0 9d 78 8a 52 cb 7e 09 5e 2e 58 47 30 a9 ed ea 1d 17 eb 4d 77 02 32 1b 0e 2d df 0e
3e 63 a4 38 79 6c 5f 0c 0c d4 e3 86 9c 77 90 77 96 d1 90 2b 78 de 16 92 32 bb f9 e4 b7 87 1f b2 51
a3 bf 9d f5 bd 3c 1b 4e 08 87 53 c0 1f 34 02 81 f9 30 80 92 be 33 97 d4 d2 4f ac 3f 8a 9e 29 c8 f7
88 56 a7 1a 40 a4 97 47 95 71 56 c4 a1 6e c4 f5 d4 1f 83 55 41 4f e0 ca 6e 2a 16 df 12 26 05 cd 91
c3 e7 e8 da 3d a0 3d 53 4a aa f6 06 5c 48 f7 20 db c4 80 fc 4d b6 a9 38 0c 9e 03 0b ed 45 c9 8b bd
e1 73 3f a8 45 54 43 c7 ca 5f 49 33 98 3a 03 43 65 82 14 16 f3 3b ec 82 2e aa 4c 8a c7 20 04 7f 57
a7 02 03 01 00 01

...same result as a Base64 string:
MIIBCgKCAQEA3o1GZDe0ivcgcWetu82mX+G7G5P9Ztsq5xptSmzL36mfyxUjrctA2MCY0n604s5Gmv3hrrYgUiRndhmITPngnXiK
Ust+CV4uWEcwqe3qHRfrTXcCMhsOLd8OPmOkOHlsXwwM1OOGnHeQd5bRkCt43haSMrv55LeHH7JRo7+d9b08G04Ih1PAHzQCgfkw
gJK+M5fU0k+sP4qeKcj3iFanGkCkl0eVcVbEoW7E9dQfg1VBT+DKbioW3xImBc2Rw+fo2j2gPVNKqvYGXEj3INvEgPxNtqk4DJ4D
C+1FyYu94XM/qEVUQ8fKX0kzmDoDQ2WCFBbzO+yCLqpMiscgBH9XpwIDAQAB

Result of a call to the toSubjectPublicKeyInfo(_:) function as an array of hex values:
30 82 01 22 30 0d 06 09 2a 86 48 86 f7 0d 01 01 01 05 00 03 82 01 0f 00 30 82 01 0a 02 82 01 01 00
de 8d 46 64 37 b4 8a f7 20 71 67 ad bb cd a6 5f e1 bb 1b 93 fd 66 db 2a e7 1a 6d 4a 6c cb df a9 9f
cb 15 23 ad cb 40 d8 c0 98 d2 7e b4 e2 ce 46 9a fd e1 ae b6 20 52 24 67 76 19 88 4c f9 e0 9d 78 8a
52 cb 7e 09 5e 2e 58 47 30 a9 ed ea 1d 17 eb 4d 77 02 32 1b 0e 2d df 0e 3e 63 a4 38 79 6c 5f 0c 0c
d4 e3 86 9c 77 90 77 96 d1 90 2b 78 de 16 92 32 bb f9 e4 b7 87 1f b2 51 a3 bf 9d f5 bd 3c 1b 4e 08
87 53 c0 1f 34 02 81 f9 30 80 92 be 33 97 d4 d2 4f ac 3f 8a 9e 29 c8 f7 88 56 a7 1a 40 a4 97 47 95
71 56 c4 a1 6e c4 f5 d4 1f 83 55 41 4f e0 ca 6e 2a 16 df 12 26 05 cd 91 c3 e7 e8 da 3d a0 3d 53 4a
aa f6 06 5c 48 f7 20 db c4 80 fc 4d b6 a9 38 0c 9e 03 0b ed 45 c9 8b bd e1 73 3f a8 45 54 43 c7 ca
5f 49 33 98 3a 03 43 65 82 14 16 f3 3b ec 82 2e aa 4c 8a c7 20 04 7f 57 a7 02 03 01 00 01

...same result as a Base64 string:
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA3o1GZDe0ivcgcWetu82mX+G7G5P9Ztsq5xptSmzL36mfyxUjrctA2MCY
0n604s5Gmv3hrrYgUiRndhmITPngnXiKUst+CV4uWEcwqe3qHRfrTXcCMhsOLd8OPmOkOHlsXwwM1OOGnHeQd5bRkCt43haSMrv5
5LeHH7JRo7+d9b08G04Ih1PAHzQCgfkwgJK+M5fU0k+sP4qeKcj3iFanGkCkl0eVcVbEoW7E9dQfg1VBT+DKbioW3xImBc2Rw+fo
2j2gPVNKqvYGXEj3INvEgPxNtqk4DJ4DC+1FyYu94XM/qEVUQ8fKX0kzmDoDQ2WCFBbzO+yCLqpMiscgBH9XpwIDAQAB

Success!

Dependencies

rsa-public-key-importer-exporter depends on the following:

• simple-asn1-reader-writer, version 0.1.0 or better.
• Swift 5.0.

Resources

A Layman’s Guide to a Subset of ASN.1, BER, and DER

X.690 (ASN.1 encoding formats: BER, DER and CER)

RFC 5280 (X.509 v3)

RFC 8017 (PKCS #1 v2.2)

License

rsa-public-key-importer-exporter is licensed under the MIT License. See LICENSE for details.