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rsa_decryption_oaep_sha1_string.md

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Cross-platform cryptography

RSA string decryption with OAEP SHA1 padding

This is the shortened version of RSA string encryption with OAEP SHA1 padding. Receiving encrypted data requires a decryption of the ciphertext. For the decryption the Private key of the recipient is used.

One note about the key management in my programs: usually the keys are (securely) stored in files or a key store and may have additional password protection. Both scenarios are unhandy in demonstration programs running in an online compiler. That's why I'm using static, hard-coded keys in my programs - please do not do this in production environment! Never ever store a Private Key in the source! The minimum is to load the keys from a secured device; simply uncomment a line in the code to load the key from a file.

steps in the program

The program follows the usual sequence:

  1. receive encrypted data in Base64 encoding
  2. start the decryption process
  3. load the Private key
  4. Base64 decoding of the ciphertext
  5. set the decryption parameters (same as used for encrypting)
  6. decrypt the ciphertext to the "decryptedtext" and show the result.

If you like to see the full encryption with decryption see my separate article RSA string encryption with OAEP SHA1 padding.

⚠️ Security warning ⚠️

This is a serious warning regarding the security of the programs shown in these article series. Always keep in mind my disclaimer regarding my programs: All programs are for educational purposes and are not intended to use in production or any other programs where a secure solution is needed. The programs do not have proper exceptional/error handling and in some cases they use insecure key lengths or other methods that are insecure. Never ever use the programs in real life unless checked by a qualified professional cryptographer.

The following links provide the solutions in code and an online compile that runs the code.

Language available Online-compiler
Java ✅ repl.it CpcJavaRsaDecryptionOaepSha1String
PHP ✅ repl.it CpcPhpRsaDecryptionOaepSha1String
C# ✅ repl.it CpcCsharpRsaDecryptionOaepSha1String
Javascript CryptoJs ❌ the encryption functionality is not available in CryptoJs
NodeJS Crypto ✅ repl.it CpcNodeJsCryptoRsaDecryptionOaepSha1String
NodeJS forge ✅ repl.it CpcNodeJsRsaDecryptionOaepSha1String
Webcrypto decryption only ✅ your browser WebcryptoRsaDecryptOaepSha1String.html
Python *1) ❌ see full version

*1) you need the external library pycryptodome, version 3.9.9

This is an output (your will differ because a random element):

RSA 2048 decryption OAEP SHA-1 string

* * * decrypt the ciphertext with the RSA private key * * *
ciphertextReceivedBase64: In0CE7VSJlr6PT+fl9SCejWhNZYioVn1UzYaqYUms7Y63oi4xK/2Qrgyi5a3CnvappM1MHdDaZVc+bDzl/iBiUslkHcF8lWGD4YdKuJgtfSS8WBRuIxz78EFhU3TfMU3y0v0bhUUj1/6ZdO/p9j8KcNbnpEB8A9YW+bZC1qOO8ibnTNbb3RHQekafz6r9oAYsILNga1pi9ZlyXQPYi7VpWAeZmUOq+MHEgD/Nkq/oxkyMo/yf5SVk1ig8M5Lr6arj22r2ePpQ8j3onmN7aOTCWUhZ7FdLm7IiRYebZ3MWPWozt9O6BSNjALLDXm7NfKaYcgQ+bVXrA4k1M9f4M9OEA==
decryptedtext: The quick brown fox jumps over the lazy dog

Last update: Jan. 29th 2021

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