Chilkat2-Python

RSA-OAEP with SHA256 hashing

See more RSA Examples

RSA encrypt a SHA256 hash with OAEP padding. Chilkat2-Python

import sys
import chilkat2

success = False

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

pubkey = chilkat2.PublicKey()

sbPem = chilkat2.StringBuilder()
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 == False):
    print(pubkey.LastErrorText)
    sys.exit()

# Build a small string to encrypt
json = chilkat2.JsonObject()
json.UpdateString("example","123")
json.UpdateString("hello","world")
print(json.Emit())

# 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 = chilkat2.Rsa()
rsa.PkcsPadding = False
rsa.OaepHash = "SHA-256"
rsa.UsePublicKey(pubkey)
rsa.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.LastMethodSuccess == False):
    print(rsa.LastErrorText)
    sys.exit()

print("Result: " + encryptedStr)