(Ruby) RSA-OAEP with SHA256 hashing

RSA encrypt a SHA256 hash with OAEP padding.

Chilkat Ruby Downloads install from rubygems.org gem install chilkat or download... Ruby Library for Windows, MacOS, Linux, Alpine Linux

require 'chilkat'

# This example requires the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

pubkey = Chilkat::CkPublicKey.new()

sbPem = Chilkat::CkStringBuilder.new()
bCrlf = true
sbPem.AppendLine("-----BEGIN PUBLIC KEY-----",bCrlf)
sbPem.AppendLine("MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA33TqqLR3eeUmDtHS89qF",bCrlf)
sbPem.AppendLine("3p4MP7Wfqt2Zjj3lZjLjjCGDvwr9cJNlNDiuKboODgUiT4ZdPWbOiMAfDcDzlOxA",bCrlf)
sbPem.AppendLine("04DDnEFGAf+kDQiNSe2ZtqC7bnIc8+KSG/qOGQIVaay4Ucr6ovDkykO5Hxn7OU7s",bCrlf)
sbPem.AppendLine("Jp9TP9H0JH8zMQA6YzijYH9LsupTerrY3U6zyihVEDXXOv08vBHk50BMFJbE9iwF",bCrlf)
sbPem.AppendLine("wnxCsU5+UZUZYw87Uu0n4LPFS9BT8tUIvAfnRXIEWCha3KbFWmdZQZlyrFw0buUE",bCrlf)
sbPem.AppendLine("f0YN3/Q0auBkdbDR/ES2PbgKTJdkjc/rEeM0TxvOUf7HuUNOhrtAVEN1D5uuxE1W",bCrlf)
sbPem.AppendLine("SwIDAQAB",bCrlf)
sbPem.AppendLine("-----END PUBLIC KEY-----",bCrlf)

# Load the public key object from the PEM. 
success = pubkey.LoadFromString(sbPem.getAsString())
if (success != true)
    print pubkey.lastErrorText() + "\n";
    exit
end

# Build a small string to encrypt
json = Chilkat::CkJsonObject.new()
json.UpdateString("example","123")
json.UpdateString("hello","world")
print json.emit() + "\n";

# This is the JSON to be RSA encrypted:  {"example":"123","hello":"world"}

# IMPORTANT: RSA encryption is only used to encrypt small amounts of data.
# RSA is only able to encrypt data to a maximum amount of your key size (2048 bits = 256 bytes) 
# minus padding / header data (11 bytes for PKCS#1 v1.5 padding, 42 bytes for OAEP).
# As a result it is often not possible to encrypt files with RSA directly. 
# RSA is also not meant for this purpose. 
# 
# If you want to encrypt more data, you can use something like:
# 1) Generate a 256-bit random keystring K
# 2) Encrypt your data with AES-CBC with K
# 3) Encrypt K with RSA
# 4) Send both to the other side 

rsa = Chilkat::CkRsa.new()
rsa.put_OaepPadding(true)
rsa.put_OaepHash("SHA-256")
rsa.ImportPublicKeyObj(pubkey)
rsa.put_EncodingMode("base64")

# Note: The OAEP padding uses random bytes in the padding, and therefore each time encryption happens,
# even using the same data and key, the result will be different --  but still valid.  One should not expect
# to get the same output.
bUsePrivateKey = false
encryptedStr = rsa.encryptStringENC(json.emit(),bUsePrivateKey)
if (rsa.get_LastMethodSuccess() != true)
    print rsa.lastErrorText() + "\n";
    exit
end

print "Result: " + encryptedStr + "\n";