# Generate Rsa Public Key From Modulus Exponent Online

**Makefile**

Online jwk to pem online, pem to jwk online. Thanks for using this software, for Cofee/Beer/Amazon bill and further development of this project please Share. Any private key value that you enter or we generate is not stored on this site, this tool is provided via an HTTPS URL to ensure that private keys cannot be stolen, for extra security run this software on your network, no cloud dependency. RSA (Rivestâ€“Shamirâ€“Adleman) is one of the first public-key cryptosystems and is widely used for secure data transmission. In such a cryptosystem, the encryption key is public and distinct from the decryption key which is kept secret (private). In RSA, this asymmetry is based on the practical difficulty of factoring the product of two large prime numbers, the 'factoring problem'. Generate RSA Public/Private Key; RSA Sign Using Private Key from.pfx/.p12 to Base64 Signature; RSA Encrypt with Modulus and Exponent. Load RSA Public Key from Hex Modulus and Exponent; RSA-OAEP with SHA256 hashing; RSASSA-PSS Algorithm with SHA256 Hashing; Signing HTTP Messages. Create RSA Public Key PEM from Modulus and Exponent value in node.js. There are no dependencies to other modules for use. This allows you to use the modulus/exponent values for validating signed value. The original code is based on the answer to this stackoverflow question. Install npm install rsa-pem-from-mod-exp Usage.

CC = clang |

CFLAGS = |

DEPS = |

OBJ = modexp2pubkey.o |

LIBS = -lssl -lcrypto |

%.o: %.c $(DEPS) |

$(CC) -c -o [email protected]$<$(CFLAGS) |

modexp2pubkey: $(OBJ) |

$(CC) -o [email protected]$^$(CFLAGS)$(LIBS) |

.PHONY: clean |

clean: |

rm -f *.o |

**modexp2pubkey.c**

#include<string.h> |

#include<openssl/rsa.h> |

#include<openssl/evp.h> |

#include<openssl/bn.h> |

#include<openssl/pem.h> |

// cheating, .. ignoring deprecation warnings |

#pragma GCC diagnostic ignored '-Wdeprecated-declarations' |

unsignedchar *base64_decode(constchar* base64data, int* len) { |

BIO *b64, *bmem; |

size_t length = strlen(base64data); |

unsignedchar *buffer = (unsignedchar *)malloc(length); |

b64 = BIO_new(BIO_f_base64()); |

BIO_set_flags(b64, BIO_FLAGS_BASE64_NO_NL); |

bmem = BIO_new_mem_buf((void*)base64data, length); |

bmem = BIO_push(b64, bmem); |

*len = BIO_read(bmem, buffer, length); |

BIO_free_all(bmem); |

return buffer; |

} |

BIGNUM* bignum_base64_decode(constchar* base64bignum) { |

BIGNUM* bn = NULL; |

int len; |

unsignedchar* data = base64_decode(base64bignum, &len); |

if (len) { |

bn = BN_bin2bn(data, len, NULL); |

} |

free(data); |

return bn; |

} |

EVP_PKEY* RSA_fromBase64(constchar* modulus_b64, constchar* exp_b64) { |

BIGNUM *n = bignum_base64_decode(modulus_b64); |

BIGNUM *e = bignum_base64_decode(exp_b64); |

if (!n) printf('Invalid encoding for modulusn'); |

if (!e) printf('Invalid encoding for public exponentn'); |

if (e && n) { |

EVP_PKEY* pRsaKey = EVP_PKEY_new(); |

RSA* rsa = RSA_new(); |

rsa->e = e; |

rsa->n = n; |

EVP_PKEY_assign_RSA(pRsaKey, rsa); |

return pRsaKey; |

} else { |

if (n) BN_free(n); |

if (e) BN_free(e); |

returnNULL; |

} |

} |

voidassert_syntax(int argc, char** argv) { |

if (argc != 4) { |

fprintf(stderr, 'Description: %s takes a RSA public key modulus and exponent in base64 encoding and produces a public key file in PEM format.n', argv[0]); |

fprintf(stderr, 'syntax: %s <modulus_base64> <exp_base64> <output_file>n', argv[0]); |

exit(1); |

} |

} |

intmain(int argc, char** argv) { |

assert_syntax(argc, argv); |

constchar* modulus = argv[1]; |

constchar* exp = argv[2]; |

constchar* filename = argv[3]; |

EVP_PKEY* pkey = RSA_fromBase64(modulus, exp); |

if (pkey NULL) { |

fprintf(stderr, 'an error occurred :(n'); |

return2; |

} else { |

printf('success decoded into RSA public keyn'); |

FILE* file = fopen(filename, 'w'); |

PEM_write_PUBKEY(file, pkey); |

fflush(file); |

fclose(file); |

printf('written to file: %sn', filename); |

} |

return0; |

} |

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### Generate Rsa Public Key From Modulus And Exponent

RSA(Rivest-Shamir-Adleman) is an Asymmetric encryption technique that uses two different keys as public and private keys to perform the encryption and decryption. With RSA, you can encrypt sensitive information with a public key and a matching private key is used to decrypt the encrypted message. Asymmetric encryption is mostly used when there are 2 different endpoints are involved such as VPN client and server, SSH, etc.

Below is an online tool to perform RSA encryption and decryption as a RSA calculator.

For Java implementation of RSA, you can follow this article.

First, we require public and private keys for RSA encryption and decryption. Hence, below is the tool to generate RSA key online. It generates RSA public key as well as the private key of size 512 bit, 1024 bit, 2048 bit, 3072 bit and 4096 bit with Base64 encoded.

By default, the private key is generated in PKCS#8 format and the public key is generated in X.509 format.

## Generate RSA Key Online

### Public Key

## RSA Encryption and Decryption Online

Below is the tool for encryption and decryption. Either you can use the public/private keys generated above or supply your own public/private keys.

**Any private or public key value that you enter or we generate is not stored on this site, this tool is provided via an HTTPS URL to ensure that private keys cannot be stolen.**

This tool provides flexibility for RSA encrypt with public key as well as private key along with RSA decrypt with public or private key.

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## Usage Guide - RSA Encryption and Decryption Online

In the first section of this tool, you can generate public or private keys. To do so, select the RSA key size among 515, 1024, 2048 and 4096 bit click on the button. This will generate the keys for you.

For encryption and decryption, enter the plain text and supply the key. As the encryption can be done using both the keys, you need to tell the tool about the key type that you have supplied with the help of radio button. By default, public key is selected. Then, you can use the cipher type to be used for the encryption. The different cipger options are RSA, RSA/ECB/PKCS1Padding and RSA/ECB/OAEPWithSHA-1AndMGF1Padding. Now, once you click the encrypt button the encrypted result will be shown in the textarea just below the button.

Remember, the encrypted result is by default base64 encoded.

Similarly, for decryption the process is same. Here, you need to enter the RSA encrypted text and the result will be a plain-text. You have both options to decrypt the encryption with public and private keys.

## References