Erlang OTP 25下的RSA加解密及密钥对生成方案

一、核心API变化说明 #

OTP 25 移除了 crypto 模块中旧的 rsa_private_encrypt/3、rsa_public_decrypt/3 等函数，统一使用 public_key 模块提供的标准API处理RSA操作。

二、生成RSA密钥对 #

1. 生成内存中的密钥对 #

直接生成2048位RSA密钥对（公钥指数用通用的65537）：

% 生成私钥
{ok, PrivateKey} = public_key:generate_key({rsa, 2048, 65537}),
% 从私钥提取公钥
PublicKey = public_key:ssh_to_pubkey(public_key:private_key_to_ssh(PrivateKey)).

2. 保存密钥为PEM文件 #

将生成的密钥持久化到文件，方便后续复用：

% 保存私钥到PEM文件
PrivatePEM = public_key:pem_encode([public_key:pem_entry_encode('RSAPrivateKey', PrivateKey)]),
file:write_file("private_key.pem", PrivatePEM),

% 保存公钥到PEM文件
PublicPEM = public_key:pem_encode([public_key:pem_entry_encode('RSAPublicKey', PublicKey)]),
file:write_file("public_key.pem", PublicPEM).

三、从PEM文件加载密钥 #

替换旧的pem_to_der用法，使用标准PEM解析流程：

加载私钥 #

{ok, PrivatePEMBin} = file:read_file("private_key.pem"),
[{'RSAPrivateKey', PrivateDER, not_encrypted}] = public_key:pem_decode(PrivatePEMBin),
PrivateKey = public_key:der_decode('RSAPrivateKey', PrivateDER).

加载公钥 #

{ok, PublicPEMBin} = file:read_file("public_key.pem"),
[{'RSAPublicKey', PublicDER, not_encrypted}] = public_key:pem_decode(PublicPEMBin),
PublicKey = public_key:der_decode('RSAPublicKey', PublicDER).

四、RSA加解密与签名验签 #

1. 公钥加密+私钥解密（保密传输场景） #

PlainText = <<"now is the time for all good men to come to the aid of their country">>,
% 公钥加密，PKCS#1 v1.5填充
Encrypted = public_key:encrypt_public(PlainText, PublicKey, [{rsa_pad, rsa_pkcs1_padding}]),
% 私钥解密
Decrypted = public_key:decrypt_private(Encrypted, PrivateKey, [{rsa_pad, rsa_pkcs1_padding}]),
% 验证结果
PlainText =:= Decrypted. % 返回true

2. 私钥签名+公钥验签（身份验证/防篡改场景） #

旧代码中的rsa_private_encrypt实际是签名操作，对应新API的sign方法：

PlainText = <<"hello">>,
% 私钥签名，SHA-256哈希+PKCS#1 v1.5填充
Signature = public_key:sign(PlainText, sha256, PrivateKey),
% 公钥验签
Verified = public_key:verify(PlainText, sha256, Signature, PublicKey),
% 验证结果
Verified. % 返回true

五、适配你提供的旧代码（OTP25兼容版） #

版本1：PEM加载+签名验签替换 #

% 加载PEM私钥
{ok, PrivatePEMBin} = file:read_file("./test_private_key"),
[{'RSAPrivateKey', PrivateDER, _}] = public_key:pem_decode(PrivatePEMBin),
PrivateKey = public_key:der_decode('RSAPrivateKey', PrivateDER),
% 提取公钥
PublicKey = public_key:ssh_to_pubkey(public_key:private_key_to_ssh(PrivateKey)),

PlainText = "now is the time for all good men to come to the aid of their country",
PlainTextBin = list_to_binary(PlainText),

% 替代旧的rsa_private_encrypt：私钥签名
Foo = public_key:sign(PlainTextBin, sha256, PrivateKey),
% 替代旧的rsa_public_decrypt：公钥验签
Bar = public_key:verify(PlainTextBin, sha256, Foo, PublicKey),
% 验证结果
Bar. % 返回true

版本2：直接用密钥参数构造密钥 #

如果要直接使用给定的指数、模数等参数：

% 构造私钥结构体
E = 257,
N = 77181119504409699204797322144340611322502523292227043692039327666381749008487,
D = 77131657261414365158890407156927969457179535804176721705182844017912686753873,
PrivateKey = #'RSAPrivateKey'{modulus = N, publicExponent = E, privateExponent = D},
% 构造公钥结构体
PublicKey = #'RSAPublicKey'{modulus = N, publicExponent = E},

PlainText = <<"hello">>,
% 签名
Enc = public_key:sign(PlainText, sha256, PrivateKey),
% 验签
DecResult = public_key:verify(PlainText, sha256, Enc, PublicKey),
% 编码为Base64
B64 = base64:encode(Enc).

注意：直接构造密钥结构体时，需确保所有参数符合RSA密钥的数学规范，否则会导致操作失败。

内容的提问来源于stack exchange，提问作者aniran mohammadpour